E . The Selection of Patients for X-ray Examinations: oocu Pfiffiim NOV 5 19.89 mm m or wmu ‘ ; The Pelvimetry Examination l UPS. DEPHRTmENT OF HEFllTH 9ND HumHN SERVICES Public Health Service - Food and Drug Hdministratlon 901 lb l‘J: L BRH PUBLICATIONS Publications of the Bureau of Radiological Health (BRH) and its components are available as paper copies from either the U.S. Government Printing Office (GPO) or the National Technical Information Service as indicated by the GPO or PB prefix, respectively, on the ordering number. Publications are also available in microfiche from NTIS at $3.50 per copy. To receive all BRH reports in microfiche, at $0.85 each, you may establish a deposit account with NTIS and request automatic distribution of "FDA/HFX" reports under the "Selected Research in Microfiche" program. Publications without GPO or PB number are available only from BRH, without charge. Addresses for ordering are: Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 201402 ($1.00 minimum order); National Technical Information Service, Springfield, VA 22161 (outside North America, prices are double those listed); and Bureau of Radiological Health, Technical Information Staff (HFX-ZS), 5600 Fishers Lane, Rockville, MD 20857. All prices are subject to change. FDA 78-8068 FDA 78—8069 FDA 79—8023 FDA 79-8033 FDA 79-8035 FDA 79-8042 FDA 79-8049 FDA 79-8050 FDA 79-8058 FDA 79-8071 FDA 79—8072 FDA 79-8073 FDA 79-80714 FDA 79-8075 FDA 79-8077 Electromagnetic Fields in Biological Media - Part I: Bioelectromagnetics (PB 285 793/AS, $6.00). A Study of the Effect of High Yield Criteria for Emergency Room Skull Radiography (GPO 017—015—00150-4, $1.10) (PB 285 094/AS, mf only). Radiological Health Training Resources 1979 (PB 300 920/AS, $7.00). Bureau of Radiological Health Publications Index (GPO 017-015-00160-1, $5.50) (PB 300 931/AS, mf only) (supersedes FDA 78-8033). Regulations for the Administration and Enforcement of The Radiation Control for Health and Safety Act of 1968 (GPO 017-012-00274-9, $2.50). CSU—FDA Collaborative Radiological Health Laboratory Annual Report 1978 (PB 80-102940, $10.00). Measurements of the Performance Parameters of Gamma Cameras: Part II (GPO 017-015-00161-0, $3.25) (PB 301 O41/AS, mf only). 10th Annual National Conference on Radiation Control - A Decade of Progress (PB 299 066/AS, $21.00). Microwave Oven Radiation - An FDA Consumer Memo (pamphlet). Handbook of Mammographic X-Ray Spectra (GPO 017—015—0015#-7, $3.00) (PB 292 001/AS, mf only). Electromagnetic Fields in Biological Media: Part II - The SCAT Program, Multilayered Spheres, Theory and Applications (PB 300 904/AS, $6.00). Leakage in the Proximity of Microwave Diathermy Applicators Used on Humans or Phantom Models (PB 291 OQl/AS, $5.00). Free—Space Electric Field Mapping of Microwave Diathermy Applicators (PB 291 OQO/AS, $6.00). Evaluation of Ohmic Instrument Company Model UPM-30 Ultrasound Power Meter (PB 292 405/AS, $5.00). Imaging Ability of Collimators in Nuclear Medicine (PB 290 954/AS, $9.00). Dosimetry - A Primer on FDA 79-8077 Supplement — Imaging Ability of Collimators in Nuclear Medicine - Supplementary Collimator Data for Rectilinear Scanners (PB 290 955/AS, $10.00). FDA 79-8078 Quantification of Current Practice in Pediatric Roentgenography for Organ Dose Calculations (GPO 017-015-00158-0, $2.00) (PB 301 120/AS, mf only). FDA 79-8079 Handbook of Selected Organ Doses for Projections Common in Pediatric Radiology (GPO 017—015—00157-1, $2.50). FDA 79-8080 Measurements of Electromagnetic Fields in the Close Proximity of CB Antennas (GPO 017-015-00155-5, $1.00) (PB 292 l+011/AS, mf only). FDA 79-8081 X—Radiation and Identification Characteristics of CRT's of Foreign Manufacture (PB 293 459/AS, $8.00). FDA 79-8082 Some Considerations of Hazards in the Use of Lasers for Artistic Displays (GPO 017-015-00156—3, $1.10) (PB 294 513/AS, mf only). FDA 79-8083 National Conference on Referral Criteria for X-Ray Examinations (GPO 017—012- 00279-0, $3.75) (PB 296 l73/AS, mf only). FDA 79—8086 Evaluation of Commercially Available Laser Protective Eyewear (PB 80-103039, 9.00). FDA 79—8087 X rays, Pregnancy and You...(brochure). HHS Publication (FDA) 80-8128 ,) Iv w / (r ‘/ 1" r L The Selection {' of Patients for X-ray Examinations: The Pelvimetry Examination. bureau oi radiological health WHO Collaborating Center for Training and General Tasks in Radiation Medicine July 1980 US. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service Food and Drug Administration “»-‘ , 1‘ Bureau of Radiological Health ' Rockville, Maryland 20857 ‘ For sale by the Superintendent oi Documonu, 17.8. Oovemment Printing omen, Washington. 0.0. 20102 WI? #0: X XD81 /‘ ?L 1557 W PUBL The opinions and statements contained in this report do not necessarily represent the views or the stated policy of the World Health Organization (WHO). ii FOREWORD The Bureau of Radiological Health develops and carries out a national program to control unnecessary human exposure to potentially hazardous ionizing and nonionizing radiations and to ensure the safe, efficacious use of such radiations. The Bureau publishes the results of its work in scientific journals and in its own technical reports. These reports provide a mechanism for disseminating results of Bureau and contractor projects. They are distributed to Federal, State, and local governments; industry; hospitals; the medical profession; educators; researchers; libraries; professional and trade organiza- tions; the press; and others. The reports are sold by the Government Printing Office and/or the National Technical Information Service. The Bureau also makes its technical reports available to the World Health Organization. Under a memorandum of agreement between WHO and the Department of Health and Human Services, three WHO Collaborating Centers have been established within the Bureau of Radiological Health, FDA: WHO Collaborating Center for Standardization of Protection Against Nonionizing Radiations; WHO Collaborating Center for Training and General Tasks in Radiation Medicine; and WHO Collaborating Center for Nuclear Medicine. Please report errors or omissions to the Bureau. Your comments and requests for further information are also encouraged. ”W {K : 7' ‘ _ ,~~ ohn C. Villfort ' Director Bureau of Radiological Health , . 1 ‘iii 31901? PREFACE The selection of patients for x-ray examinations is a key factor in the radiological process, initiating events which will produce radiation exposure of the patients and generate radiological information. The questions involved, such as whether an x-ray examination is needed, what type, and how the information generated will help in patient management, often have no straightforward answers. The Food and Drug Administration's Bureau of Radiological Health supports several efforts to investigate the effectiveness of certain x- ray examinations in providing clinical information needed to aid physicians in patient care decisionmaking. One particularly significant effort involves panels of physicians convened by the Bureau to discuss certain specific medical radiation examinations and to suggest referral criteria or statements on use for them. This approach was endorsed by the National Conference on Referral Criteria for X-Ray Examinations, held in October 1978 (HEW publication (FDA) 79-8083) and attended by members of many medical specialty organizations, the legal profession, third party carriers, government agencies and consumers. The Conference attendees suggested that the private sector develop referral criteria with the government acting as a facilitator. They also recommended that referral criteria, developed by small panels of experts, be reviewed by relevant medical specialty organizations, and that the process be coordinated by the American College of Radiology and the Bureau of Radiological Health. The pelvimetry x-ray examination is the first medical radiation procedure to be considered by a Bureau—convened physician panel. The panel, composed of obstetricians and radiologists, evaluated the available literature on the efficacy of pelvimetry and drafted a statement on use which summarized its findings. The panel statement was then reviewed by the American College of Radiology and the American College of Obstetricians and Gynecologists. Although formal endorsement by medical organizations is not a necessary element in the general referral criteria effort, these two organizations did so in this case, and their formal policies appear in this document. The pelvimetry statement is the first in an anticipated series of referral criteria or statements on use that will be developed by various panels evaluating the use of specific diagnostic radiological procedures. We hope that the statements and the accompanying background material will be of value for medical students, practicing physicians, and other persons interested in the efficacious use of medical radiation. We also encourage interested parties to read the related general document "The Selection of Patients for X—Ray Examinations" (HEW Publication (FDA) 80-8104). / . William S. Properzio, . Director Division of Training and Medical Applications iv CONTENTS Page FOREWORD.............................. iii PREFACE............................... iv ACKNOWLEDGMENTS......................... vi INTRODUCTION............................l THE PELVIMETRY X-RAY EXAMINATION . . . . . . . . . . . . . . . . 2 REVIEWOFTHELITERATURE..................... 2 STATEMENTON THE USEOFX-RAY PELVIMETRY- . - - . . - . . . - . 3 REFERENCES............................. 5 APPENDIX-occaoocoo-uoonus-ounc-oon-oou 8 ACKNOWLEDGMENTS The following individuals contributed substantially to the preparation of "The Selection of Patients for X-Ray Examinations: The Pelvimetry Examination." Pelvimetry Panel Reynold F. Brown, M.D., FACR - Chairman John W. Shaver - Executive Secretary Clay R. Burchell, M.D., FACOG John A. Campbell, M.D., FACR Sergio E. Fabro, M.D., FACOG Kevin M. Kelly, M.D. Samuel H. Madell, M.D., FACR Ervin E. Nichols, M.D., FACOG Bureau of Radiological Health Joseph S. Arcarese, M.S. Gordon C. Johnson, MD. James L. Morrison, M.S. Harvey Rudolph, Ph.D. Phyllis Segal, B.A. v1“ THE SELECTION OF PATIENTS FOR X-RAY EXAMINATIONS: THE PELVIMETRY EXAMINATION INTRODUCTION Diagnostic x rays are extremely important for physicians in defining the type and extent of disease in a wide variety of clinical situations. However, due to public and professional concern over the potential risks of radiation exposure, the use of diagnostic x rays has long been studied for ways of reducing unproductive radiation exposure. Although significant reductions have occurred and will continue to occur with advances in technology, x-ray examinations of necessity involve some unavoidable x-ray exposure of the patient. Consequently, physicians are faced with the dilemma that immediate clinical benefits from diagnostic x-ray information on their patients may be accompanied by some risk of long- term adverse health effects. This places increased significance on their judgment about whether or not the examinations ought to be conducted, based upon whether the examination results are expected to aid in determining future patient care. Moreover, professional, patient, and medico-legal pressures complicate the situation and sometimes influence physicians to refer patients for x-ray examinations they might otherwise consider unnecessary. One approach to this problem which has been recommended by a number of clinicians is the development and use by referring physicians of carefully developed statements on use, or referral criteria, for those particular examination circumstances where the diagnostic benefits are unclear or questionable. Such guidelines could be helpful to physicians in deciding when to obtain x-ray examinations. Guidelines should be developed by consolidating the experience of many practitioners and they should be validated by testing in a variety of clinical settings. The use of appropriate referral criteria could minimize those instances in which the results of the diagnostic x-ray examination prove not to be helpful in patient care decisionmaking. It is also possible that the availability of referral criteria could assist physicians in resisting any real or perceived external pressures to order diagnostic x rays against their clinical judgment. This in turn could reduce medical radiation exposure to the population and help improve the use of our national health care resources. Several investigators have conducted studies that demonstrate the value of referral criteria in terms of increased clinical productivity, as well as in reduced radiation exposure to patients and reduced economic costs. For example, Bell and Loop (1) derived a high-yield criteria list designed to increase the yield of significant findings from skull x-ray examinations following trauma. They noted that if skull examinations had been ordered only on patients meeting one or more of the high-yield criteria, 92 of 93 fractures would have been detected, and that a 29 percent reduction in x-ray examinations would have been achieved without adverse effect on patient care. Phillips (2), and others, have applied and extended the work of Bell and Loop. Phillips achieved a 39 percent reduction in the number of skull x rays ordered in the emergency room of the University of Washington hospital, despite a limited compliance rate among referring physicians of only 55 percent. In 1978, a National Conference on Referral Criteria for X-Ray Examinations was cosponsored by Congressman Paul Rogers and the Secretary of Health, Education, and Welfare (3). The conference brought together representatives of health-related government agencies, State health departments, medical professional organizations, third party carriers, and the legal profession. A forum was provided for the exchange of ideas and discussion of causes of x-ray overuse and the role of x-ray referral criteria in containing x-ray exposure and health care costs. Workshop sessions were held to address specific issues in detail and to formulate plans whereby government and the private sector could work cooperatively to provide solutions. A principal recommendation emanating from the conference was that small physician panels, composed of representatives of the appropriate medical specialty societies, with government acting as a facilitator, should be convened to develop referral criteria for specific diagnostic x-ray examinations. Subsequent to that conference and in accord with its recommendations, several panels were constituted and meetings were held to discuss particular examinations. The examinations were selected on the basis of a number of criteria, including volume, available literature, and radiation exposure. One panel has considered the utility of the pelvimetry x- ray examination. Pelvimetry panel members included representatives from the American College of Radiology and the American College of Obstetricians and Gynecologists, with observers from the Food and Drug Adminstration's Bureau of Radiological Health. THE PELVIMETRY X-RAY EXAMINATION Pelvimetry is a radiographic examination used to visualize and measure the dimensions of the maternal pelvis and fetal head prior to childbirth. The rationale for the examination is to measure the birth canal and fetal head so that a judgment can be made regarding the likelihood of difficulty with the passage of the fetal head through the pelvis. Refinements and variations in technique have been introduced in the years since the examination was first performed. At least two orthogonal views are required for all techniques. Pelvimetry usually records measurements at three levels-- the pelvic inlet (upper boundary of the pelvic cavity), the mid-pelvis, and the pelvic outlet (lower boundary of the pelvic cavity). The anterior/posterior and transverse diameters at these anatomic locations are estimated from the films, as is the maximum diameter of the fetal skull. Cephalopelvic relationships and possible disproportion are estimated. Ancillary pelvimetry findings may be fetal abnormalities, fetal position and presentation, and/or other pelvic abnormalities. Since the entire maternal pelvis and at least part of the abdomen is radiographed directly, the fetus receives essentially a whole-body, direct exposure, attenuated by the overlying maternal tissues. According to the 1977 UNSCEAR Report, the mean fetal whole body dose is estimated at about 620 mrad from the pelvimetry examination (4). In the United States, pelvimetry is, in fact, the major single source of ionizing radiation to the fetus (5). A study of selected information by Kelly et al., from approximately 68,000 single deliveries in 16 teaching hospitals in the United States during 1969 and 1970, estimated that pelvimetries were performed in 6.9 percent of these deliveries (6). This rate is similar to the 5.1 percent found in a 1963 United States Public Health Service national survey of medical x-ray visits and examinations during pregnancy. Current estimates are that the pelvimetry rate is still about 6 percent of all live births in the United States, although rates at some facilities have been found to be several times greater (5,6). REVIEW OF THE LITERATURE The pelvimetry examination was one of the first examinations to be considered by a panel because several studies have suggested that the pelvimetry examination is rarely indicated for patient management and that the examination constitutes the largest source of radiation exposure to fetuses in the United States. For example, the 1975 study by Kelly et a1. provided information on the indications for and benefits of pelvimetry. The study was unable to demonstrate the value of pelvimetry in altering the course of labor (ll). (Since pelvimetry examinations are intended to be used in deciding whether or not to perform a cesarean section, it might be expected that there would be some relationship between pelvimetry rates and cesarean section rates. Kelly's study showed little or no consistent relationship between the pelvimetry and cesarean section rates at the hospitals in that study.) Joyce and colleagues stated that "antenatal pelvimetry is rarely justified, except in 2 breech presentation" (7). Campbell noted a lack of correlation between pelvic measurements and the course of labor (5). He found that the incidence of a truly "small" pelvis in patients selected for pelvimetry was as low as one or two cases in 2500. Furthermore, according to Campbell, the effects of molding of the fetal head and expansion of the maternal pelvis during labor may render pelvic diameter measurements meaningless. (For ease of reference, reports of the pelvimetry studies cited above have been included in the Appendix to this publication.) More recently, Radomsky and Radomsky have suggested that, unless pelvimetry is reserved for those rare cases where obstetric management will be based upon knowledge of internal pelvic diameters, the infant is subjected to potential hazard without corresponding benefit to the infant or mother (8). There is a considerable body of evidence that ionizing radiation exposure of humans involves potential for long-term biological injury. Exposure of the fetus is of special concern. For example, the data from the Oxford Survey of Childhood Cancers (9,10,11) have suggested that radiation exposure in utero increases the cancer risk by 50 percent during the first 15 years of the child's life. A study by MacMahon in the United States (12) also showed an increased risk of leukemia in children who were exposed in utero to diagnostic x rays. In addition to an increased risk of childhood cancer, which is a somatic effect, irradiation during pregnancy may also be associated with genetic effects. When gonadal (germ cell) tissue is irradiated, there may be mutations which give rise to changes that can be transmitted from generation to generation. Such mutations are generally assumed to be detrimental and to increase undesirable genetic characteristics in the population. STATEMENT ON THE USE OF X-RAY PELVIMETRY X-ray pelvimetry was selected for review as a result of surveying the available literature, which reflects a limited usefulness of x-ray pelvimetry and points out the potential biological ramifications of fetal radiation exposure. In accordance with recommendations made at the National Conference on Referral Criteria for X—Ray Examinations, a panel was established to examine the available information on pelvimetry. The panel, convened under a Food and Drug Administration contract with the Radiological Health Sciences Education Project, University of California, was composed of members of the American College of Radiology and the American College of Obstetricians and Gynecologists. The panel met on two separate occasions to consider pelvimetry referral criteria. A statement concerning the use of x-ray pelvimetry was developed and unanimousl endorsed by the panel. The American College of Radiology has adopted the statement {13) and the American College of Obstetricians and Gynecologists has adopted a similar statement (11+). The Food and Drug Administration, Public Health Service, is publishing the pelvimetry statement as the first in. an anticipated series concerning various diagnostic x-ray examinations, in accordance with recommendations of the National Conference on Referral Criteria for X-Ray Examinations. It is intended that subsequent statements on uSe/referral criteria will be developed in a manner similar to that utilized in the development of the pelvimetry statement. This process involves a close, cooperative interchange between the Public Health Service, the American College of Radiology, and other relevant professional societies, utilizing available scientific literature, and searching for possible clinical consensus. The statements/referral criteria and the rationale for their development will be made readily available to concerned persons for the purpose of stimulating additional research and providing valuable information for clinicians. After thorough review of the available evidence, the following statement was developed and approved by the Food and Drug Administration's panel on x-ray pelvimetry on January 26, 1979: "Pelvimetry is not usuall necessary or helpful in making the decision to perform a cesarean section. There ore, pelvimetry should be performed only when the physician caring for the patient feels that pelvimetry will contribute to the decisions concerning diagnosis or treatment. In those few instances, the reason for requesting the pelvimetry should be written on the patient's chart. This statement does not apply to x—ray examinations for purposes other than measurement of the pelvis." This statement subsequently was approved and adopted by the American College of Radiology. The American College of Obstetricians and Gynecologists has approved the following statement which it interprets as comparable to the panel statement: "X-ray pelvimetry provides limited additional information to physicians involved in the management of labor and delivery. It should not be a prerequisite to clinical decisions concerning obstetrical management. Reasons for requesting x—ray pelvimetry should be individually established." It is the intent of the undersigned that the pelvimetry statement serve as a guide for clinical studies and, if affirmed, become a model for good radiological practice. Date Robert C. Cefalo, M.D. Chairman, Committee on Obstetrics: Maternal and Fetal Medicine American College of Obstetricians and Gynecologists Date . Robert D. Moseley, Jr., M.D. Chairman, Radiation Advisory Committee American College of Radiology Date ohn C. Villfor Assistant Surgeon General and Director, Bureau of Radiological Health 5. 10. 11. 12. 13. 14. REFERENCES Bell, R.S. and Loop, J.W. The utility and futility of radiographic skull examinations for trauma. N Engl J Med 284:236—239 (February 1971). Phillips, L.A. A study of the effect of high yield criteria for emergency room skull radiography. HEW Publication (FDA) 78-8069 (July 1978). National Conference on Referral Criteria for X-Ray Examinations held in Washington, D.C., October 25-27, 1978. HEW Publication (FDA) 79—8083 (April 1979). United Nations Scientific Committee on the Effects of Atomic Radiation 1977 Report to the General Assembly. Sources and Effects of Ionizing Radiation. United Nations, New York (1977). Campbell, J.A. X-ray pelvimetry: Useful procedure or medical nonsense. J Natl Med Assoc 68:5114-520 (November 1976). Kelly, K.M., Madden, D.A., Arcarese, J.S., Barnett, M. and Brown, R.F. The utilization and efficacy of pelvimetry. Am J Roentgenol 125:1:66—7‘1 (September 1975). Joyce, D.N., Giwa-Osagi, F. and Stevenson, G.W. Role of pelvimetry in active management of labour. Br Med J l+:505—507 (November 1975). Radomsky, J.W. and Radomsky, N.A. Efficacy of pelvimetry. J Can Med Assoc 31:43- “ (March 1980). 0 Stewart, A., Webb, J., and Hewitt, D. A survey of childhood malignancies. Br Med J 1:1495 (1958). Bithell, J. and Stewart, A. Prenatal irradiation and childhood malignancy: A review of British data from the Oxford Survey. Br J Cancer 31:271-278 (1975). Kneale, G.W. and Stewart, A.M. Mantel-Haenszel analysis of Oxford data. 1. Independent effects of several birth factors including fetal irradiation. J Natl Cancer Inst 56:879-883 (1976). MacMahon, B. Prenatal x—ray exposure and childhood cancer. J Natl Cancer Inst 28:1173 (1962). The American College of Radiology Bulletin, 2, (October 1979). ACOG Newsletter 23:10, 11:2 (October/November 1979). APPENDIX Reprinted from The American Journal of Roentgenology, Radium Therapy and Nuclear Medicine Vol. 125, No. 1,September, 1975 PRINTED U.I.A. THE UTILIZATION AND EFFICACY OF PELVIMETRY* By KEVIN M. KELLY, M.D.,1‘ DALE A. MADDEN, M.S., JOSEPH S. ARCARESE, M.S., MARK BARNETT, M.S., and REYNOLD F. BROWN, M.D. ROCKVILLE, MARYLAND ABSTRACT: Data from non random groups of deliveries with some identical clinical factors were compared and certain conclusions are suggested. Most x-ray examinations which cause significant fetal exposure are pelvimetries- There appears to be no uniform set of indications for performing pelvimetry. Instead, the criteria seem to vary from hospital to hospital and even from physi— cian to physician within the same hospital. A normal pelvimetry gives the physi— cian little confidence that a cesarean section will not be necessaryl The duration of labor is not significantly altered by pelvimetry in those cases needing a cesarean section for cephalopelvic disproportion or following unsuccessful oxytocin stimu— lation. OENTGENOGRAPHIC evaluation of the relative sizes of the fetal head and maternal pelvis has been used clinically almost since the advent of medical radiog— raphy. The technique was considerably re- fined by Colcher and Sussman in 1944.5 Further refinements and variations have been instituted since that time.""“"’v7v”-12 Even though pelvimetry has been widely used over the years and has been generally accepted as a clinical tool, its efficacy has been questioned recently by some authori- ties.3'“-”-“ Any doubts about the useful— ness of this procedure assume additional significance in light of evidence that irradi- ation of the fetus, even at the low levels used in diagnostic radiology, may carry with it an increased risk of leukemia and other malignant tumors in childhood.3-‘°""" Because of these questions of risk and eflicacy, a study of selected information from 67,078 single deliveries in the years 1969 and 1970 was undertaken to evaluate the utilization and efficacy of pelvimetry. This information was collected and pro- vided by the Obstetrical Statistical Cooper— ative based at Downstate University in Brooklyn, New York. The Cooperative is an association of teaching hospitals which collects data on all deliveries at these hospitals for later use in retrospective in- vestigation by any member institution. MATERIAL AND METHOD This study analyzed clinical information from 67,078 single deliveries of 1,000 gm. or greater from 16 hospitals. Pelvimetries were performed during 6.9 per cent (4,599) of these deliveries, a rate which is similar to the 5.1 per cent foundin a 1963 U.S.P.H.S. national survey.” The cases, although con- stituting about 1 per cent of the deliveries in the United States for 1969 and 1970, do not constitute a representative sample in a number of ways. As illustrated in Table 1, the population studied differed consider— ably from what would be expected in a random national sample in many geo- graphical, economic and racial factors. Also, all of the hospitals providing data in this study were training institutions; con— sequently, a greater proportion of the deliveries were assisted by interns and resi— dents than would be expected on a national basis. The Cooperative case record consists of approximately 75 datum elements, the most pertinent of which are listed in Table ' From the Bureau of Radiological Health and Office of Special Studies, Food and Drug Administration, U.S. Public Health Service, Department of Health, Education, and Welfare, Rockville, Maryland. l' Current Address: Department of Radiology, St. Francis Hospital, Lynwood, California. 66 Reprinted by permission of the American Roentgen Ray Society. The Williams & Wilkins Company (agent) VoL. us, No. I The Utilization and Efficacy of Pelvimetry TABLE I nus or DATA 67 Obstetrical Statistical Cooperative Population National Population (I. 18) 1. Geographical 2. Economic 3. Racial 4. Type of Care 90 per cent deliveries from New York City Area 69 per cent deliveries from inner cities 70 per cent ward patients 4.3 per cent non-white 100 per cent teaching hospitals 69 per cent trainee deliveries 5.3 per cent <3o per cent est. 29 per cent 17.2 per cent 4! .7 per cent est. 29 per cent 5. Parity 100 per cent single births 97 .5 per cent II. The attending physicians abstracted the clinical data onto; a data form. This form was checked for completeness by one per- son, generally a medical secretary, at each participating hospital and the information transferred to magnetic computer tape. GOALS AND LIMITATIONS OF THE STUDY The data accumulated through this study provide direct information on the frequency ofpelvimetry use, at least among the participating hospitals. But the more important questions of “Why is pelvimetry done?" and “Is there any benefit from the procedure?” cannot be answered directly by this study, since the data collection system did not ascertain the attending physician’s indications for the pelvimetry, nor his own direct evaluation of its useful- ness in each case. However, the study was used to extract information indirectly on the indications for and benefits from pelvim— etry. With respect to indications, certain clinical conditions associated with high rates of pelvimetry were identified by computer, enabling us to infer that these conditions were commonly employed in- dications for the x—ray procedure. We were able to derive answers to the question of benefit by observing whether some of the commonly assumed goal: of pelvimetry (a shortening of nonproductive labor in cer- tain clinical circumstances, for example) were actually accomplished in x—rayed women as compared with those who had not had pelvimetry. TABLE II PARTIAL LIST OF DATA AVAILABLE ON PATIENTS IN THE STUDY . Pelvimetry Other X-ray Examinations . Method of Delivery Complications of Delivery Complications of Pregnancy . Position of Fetus . Type of Pelvis . Prior Pregnancies . Prior Abortions . Prior Fetal Deaths . Prior Medical Diseases . Prior Surgery . Present Medical Diseases Swanqoup-g-wp— an 9— u L.) 14. Reason for Operative Intervention 15. Age of Mother 16. \Veight of Mother 17. Height of Mother 18. Race of Mother 19. Weight Gain of Mother 20. \Vceks of Pregnancy 2.1. Birth Weight 7.2. Anomalies 23. Resuscitation 24. Infant Diseases 25. Reason for Neonatal Death 68 Kelly, Madden, Arcarese, Barnett and Brown One further word of caution is necessary. This study is an evaluation of the effect of pelvimetry on groups and not on indi— viduals. As in the case of any statistical investigation, some individual patients may prove to be exceptions to the general- izations drawn from the study. DISCUSSION 1. Pelvimetry a: a contriautor to fetal irradiation. Simple tabulation of the data showed that pelvimetries accounted for 72 per cent of all the examinations which de— livered direct x-ray exposure to the fetuses in this study. In other words, nearly three— fourths of the pelvic and abdominal x-ray procedures in the study were pelvimetries. This is considerably higher than the 50 per cent reported in the 1963 U.S.P.H.S. study.” This difference may be explained by the substitution of ultrasound for many nonpelvimetric x—ray examinations of preg— nant women since 1963. Consequently, pelvimetry may now have emerged as the greatest single source offetal iwadiation by for. As ultrasound becomes more and more widely available, this phenomenon can be expected to continue. 2. Indications for pelvimetry. As men- tioned above, the question of ”Why is pelvimetry done?” was not directly answer— able because the physicians reasons for requesting pelvimetry were not recorded in the original data. However, a decision analysis computer program15 was used to weigh the relative importance of the re- corded clinical factors associated with pelvimetry. This generated a decision tree which revealed some of the reasons for the pelvimetries, as shown in Figure I. The computer program divided the deliveries first into 2 subgroups; each subgroup was then divided into 2 others, etc. This di- vision process continued until little addi- tional variation in pelvimetry rates could be explained by further subdivision. Each division was based on the clinical factor that would give the highest possible pelvim- etry rate in the subgroup with that fac- tor and the lowest rate in the subgroup 10 SEPTEMBER, 1975 without it.* For example, uterine dysfunc- tion was the first determinant chosen by the computer program because it was the clinical factor which best divided the de- liveries into high and low pelvimetry rate subgroups. The program then treated each of these two subgroups separately and divided them again on the next most im- portant factor (fetal position), and so on. The reasons for pelvimetries which were discovered by the process are summarized in Table III. They can be divided into 3 categories: (I) patient—related indications important in most cases; (2) physician-re— lated factors important in most cases; and (3) patient—related indications important in only a limited portion of the study popu— lation. The fact that the computer pro- gram selected physician-related factors (the experience of the attendant physician at delivery and the particular hospital in which the pelvimetry was done) seems to indicate that pelvimetries may not be ordered solely on uniform and objective clinical grounds. In addition, it was par- ticularly disquieting that only 20 per cent of the variation in whether or not pelvim— etries were ordered could be explained by the decision analysis program. The re— maining variation appeared to be due to a lack of consistency within the data them- selves. In other words, the most important determinants in the decision to use pelvim- etry seem not to be consistent clinical factors or combinations of factors, but rather the variation ofattending physicians in identical clinical circumstances. 3. Pelvimetry and remrean section rates. The pelvimetry rate varied from 1.8 per cent to 15.7 per cent among the 16 hospitals studied. Since pelvimetric examinations serve primarily as an aid in deciding whether or not to perform a cesarean sec— tion, it might be expected that there would be some relationship between pelvimetry ' More accurately. the program uses :1 standard least squares method to mmimize the e\pl11ned \uri1tio.1 “ith pelvimetry taking on \ :Ilues I (yes) or o (no), the e\pl:\incd vari. It. on is the ratio of the sums of the squares of the deviations from the final group means to the sum of the squares of the deviations from the original group mean. VoL. us, No. 1 The Utilization and Efficacy of Pelvimetry P" EELVIMETRY DATA ANALYSIS DECISION PROCESS 6.9% PELVIMETRY 67.073 DELIVERIES REs. 2: OTHER RES. 3: OTHER NO :3 3 YES —0 —1 O O 2' 9; =° =° O U '0 ‘U > > 33 I! 44.57. 5 22.09. 20.4». 3 7.90. g", 50'. 5.29. g 13*‘ 1.333 957 3.550 2.303 5.325 15.333 32.390 NONE. g NONE. LT.PD. OTHER DYSF- < ELECT- 13.7 RUP. LT. PD NONE 3 MEMB 13—7' RUP' OTNE'R _ g - 2 NENB. 50.0% 24.32. 43.01. 12.59 37.3.. 10.2% 32.49. 5.2% 7.9% 1.03 . 1,434 399 914 2.335 1,301 1.075 033 15.195 1,132 31,714 0 8 YES 3‘ NO NO YES MEET?" 3 2,7,; . 8 PRIOR ~ 5 ' Hosp. 1.- PREG. 2 01.33 43.4% 55.43 13.53 53.91. 32.2% 51.33 15.3% . 333 1.043 606 303 421 1.330 304 334 .- HOSP. HOSP. 55.9% 29.5% 75.9% 35.57. 1 551 495 310 295 —# 4- I FIG. 1. Decision tree, generated by decismn analysrs computer program. This shows the major factors which accounted for some of the variation in the use of pelvimetry in the study hospitals. 11 70 Kelly, Madden, Arcarese, Barnett and Brown Serreulza, :97; TABLE III IMPORTANT FACTORS IN THE DECISION TO DO A PELVIMETRY 1. Patient related factors important in most cases (A) Strength of uterine contractions (B) Position of the fetus (C) Any prior term pregnancies a. Physician related factors important in most cases (A) Experience of the attending physician (B) Hospital or departmental practice 3. Patient related factors important in select cases (A) Premature rupture of the membranes (B) Length of labor (C) Use of oxytocin (D) Toxemia (E) Weeks of pregnancy rates and cesarean section 'rates at the various hospitals. In fact, the correlation coefficient was 0.28, which is not signifi- cantly different from o. This shows that there was little or no consistent relationship between the pelvimetry and cesarean sec— tion rates at the hospitals in the study. This is graphically demonstrated in Figure 2. Since there was considerable variation among the hospitals in the rate of prima- gravid women coming to delivery, it might be argued that a hospital with a higher per- centage of primagravid women might have a relatively high rate of pelvimetry which would contribute to lack of correlation shown above. However, when the pelvim- etry rate was compared to the cesarean rate for all 16 hospitals, for those women who had never previously had a term pregnancy, the correlation coeflicient was even lower (0.11). i‘ 4. Eflectivenu: q/pelvimetry. The marked variability in the use of pelvimetry among physicians in similar clinical situations, along with the lack of correlation between pelvimetry use and cesarean rate, raised the question of whether pelvimetries were beneficial at all. Since pelvimetry should be used only for comparative measurements of the fetal head and maternal pelvis in order to determine whcther safe vaginal 12 delivery is possible, the fundamental ques- tion is whether the physician can make this decision more accurately and more quickly with the aid of pelvimetry than would be possible using clinical judgment alone. a. Prognostic value ofthe normal pelvim- etry. The data show that 41 per cent of patients undergoing cesarean section re- ceived a pelvimetry. Among those who had a pelvimetry which was interpreted as normal, 27 per cent nonetheless went on to have a section. One of the arguments in favor of pelvimetry has been that when the clinician has roentgenographic confirma— tion of a normal pelvis, he is able more judiciously to allow labor to progress. How- ever, these findings contradict this. The decision to do a pelvimetry puts a woman in a class with a high rate of cesarean sec- tions, about 4 out of 10. The finding that her pelvis is normal reduces her chance of cesarean section slightly (to about 3 out of 10). In other words, because a signifi- cant chance of cesarean section still exists in women with a normal pelvimetry, the clinician still has to make the same deci- sion about cesarean section on clinical grounds that he would have had to make even if he had not done the pelvimetry in the first place. b. Prognostic value of pelvimetry in cephalopelvic disproportion. If pelvimetry helps to provide an early and accurate diagnosis of cephalopelvic disproportion and thus allows for timely intervention with cesarean section, then women with disproportion who have had pelvimetry should undergo, on the average, a shorter labor prior to section than those with dis- proportion who have not received pelvim- etry. \Vith this in mind, the duration of labor was compared for 2 groups of pa- tients in the study: those diagnosed as hav— ing cephalopelvic disproportion and under- going cesarean section who had received a pelvimetry, and those with the same diag— nosis and section who had not had a pel- vimetry. To make the groups more alike, Von. 125, No. 1 16 15 14 13 12 11 H a o I a I I ~ N l I PERCENT OF DELIVERIES The Utilization and Efficacy of Pelvimetry 7I PELVIMETRY AND CESAREAN SECTION RATES IN 16 HOSPITALS AVERAGE CES. RATE I \ CESAREAN I I I | I I \ PELVIMETRY HOSPITAL FIG. 2. Comparison of pelvimetry and cesarean section rates found in 16 member hospitals of the Obstetrical Statistical Cooperative. only women both delivering for the first time and having infants greater than 2,500 gm. were included. As shown in Figure 3, there was essentially no difference between the two groups with respect to hours of labor. In other words, as it was used in the 16 hospitals, pelvimetry did not significantly shorten labor in those women with cephalo- pelvic disproportion when compared to the use of clinical judgment alone. c. Prognostic value of pelvimetry on oxytocin failures. Since a pelvimetry is done to prevent those with a pelvis inade- 13 quate for vaginal delivery from having an unnecessarily long labor, only data con- cerning the oxytocin failures are presented here (Fig. 4 and 5). Two separate groups, those having elective stimulation and those having stimulation for dysfunction were considered. First, patients having an un‘ successful elective oxytocin stimulation, with or without pelvimetry, were com- pared to see if pelvimetry shortened the duration of labor prior to cesarean section. Again, only those women with at least a 2,500 gm. fetus and who had not had a 72 Kelly, Madden, Arcarese, Barnett and Brown Sznzunn, 1975 CESAREAN SECTIONS REQUlRED BECAUSE OF DISPROPORTION 16 - ‘—N0 PELVIMETRY MEAN=1L4 HRS “V; (219 DELlVERIES) MEDIAN=!0.0 HRS E g 3 12 - LIJ D IL 0 E \ S 8 >— \ K \ if V’ PELVIMETRY MEAN: 11.8 HRS ‘ (1008 DELIVERIES) MEDIAN:11.0 HRS 4 — l 1 1 l 1 J L l 1 l J 0 1 3 5 7 9 11 13 15 17 19 21 23 25 Z] 29 33 2 4 6 8 10 12 14 16 18 20 22 24 26 28 32 + HOURS OF LABOR FIG. 3. Comparison of duration of labor experienced by patients, with and without pelvimetry, who had cesarean sections because of cephalopelvic disproportion. previous term pregnancy were used in this comparison so that the groups would be composed of similar individuals. Figure 4 reveals no significant difference between the 2 groups. . Next, the patients with unsuccessful oxytocin stimulation for dysfunction were considered. Duration of labor for these women is shown in Figure 5. The mean and median labor lengths for the women with pelvimetry were about 2 hours longer than those without pelvimetry. A number of factors could account for this. For exam— ple, the longer length of labor among the x-rayed women might be related to the time consumed in ordering, performing, and interpreting a pelvimetry; in many hospitals it may take up to an hour or more to transport the patient to the x-ray de- partment, carry out the procedure, and return her to the delivery suite. Some of the delay in performing necessary cesarean sections among the x-rayed women may be related to indecisiveness or procrastination on the part of those physicians who most 14 often use pelvimetries. This suggestion is supported by the computer decision analy- sis which showed a greater use of pelvime— try by the less experienced attendant physicians. It should be noted that any difference between the pelvimetry and non—pelvime- try groups in this study could possibly be accounted for by a basic difference be- tween the groups beyond the fact that some were x-rayed and others were not; retrospective studies such as this are par- ticularly prone to such difficulties. For example, differences in duration of labor among the pelvimetry and non-pelvimetry groups could be due to a greater propor— tion of difficult cases, i.e., those in which a clinical decision is harder to make, within the pelvimetry group. But it is difficult to imagine enough variation in the distribu— tion of "difficult cases" among the 16 hos— pitals in the study to account for the nine- fold variation in the use of pelvimetry ob— served among them. In any case, as can be seen from Figures VOL. 12;, No. x The Utilization and Efficacy of Pelvimetry 73 24 ' CESAREAN SECTION FOLLOWING UNSUCCESSFUL ELECTIVE OXYTOCIN STIMULATION 20 - N0 PELVIMETRY MEAN: 11.1 HRS 3 (41 DELIVERIES) MEDIAN=11.0 HRS E 16 - u 2 .1 Lu D L O I; 12 - “.1 O K Lu L 8 - ,\ PELVINIETRY MEAN=1L1HRS ‘ \/(62 DELIVERIES) MEDIAN=10.0 HRS \ I \ \ A 4 _ / /’\ \ \ I AI 7 9 11 13 15 17 19 21 23 25 TI 29 33 2 4 5 8 10 12 14 16 18 20 22 24 26 28 32 + HOURS OF LABOR FIG. 4. Comparison of duration of labor experienced by patients, with and without pelvimetry, who had cesarean sections following unsuccessful oxytocin stimulation. The difference at 0 hours between the 2 groups is due only to 3 patients and is not statistically significant. 15 .. CESAREAN SECTION FOLLOWING UNSUCCESSFUL OXYTOCIN STIMULATION FOR DYSFUNCTION NO PELVIMETRY MEAN=15.1 HRS (108 DELIVERIES) MEDIAN=14.0 HRS 12- /-—— PELVIMETRY MEAN = 17.0 HRS I (175 DELIVERIES) MEDIAN=16.0 HRS PERCENT OF DELIVERIES on 1 ’/ I/ I I I I I 1 I I I I L 0 l 3 5 7 9 11 13 15 17 19 21 23 25 27 29 33 2 4 6 8 10 12 14 16 18 20 22 24 26 28 32 4- HOURS OF LABOR FIG; 5. Comparison of duration of labor experienced by patients, with and without pelvimetry, who had cesarean sections, following unsuccessful oxytocin stimulation for uterine dysfunction. 15 74 4 and 5, pelvimetry did not decrease the length of labor in those who ultimately went to cesarean section following unsuc- cessful oxytocin. The authors feel that the findings from this study warrant a prospective investiga- tion of the efficacy of pelvimetry. Kevin M. Kelly, M.D. Department of Radiology St. Francis Hospital 3630 Imperial Highway Lynwood, California 90261 REFERENCES . American Hospital Association, Chicago, Illinois. Personal correspondence concerning statistics for 1970. . BORELL, U., and RADDERO, C. Orthodiagraphic pelvimetry with special reference to capacity of distal part Of pelvis and pelvic outlet. Ada radial. (Diag.), 1964, 2, 273—282. . BRoss, I. D. J., and NATARAJAN, N. Leukemia from low-level radiation, identification of susceptible children. New England 7. Meat, 1972,287, 107—110. . BROWN, R. C. Modification of Colcher-Sussman technique Of x—ray pelvimetry. AM. J. ROENT- GENOL., RAD. THERAPY 81 NUCLEAR MED., 1972, 115, 623-629. . COLCHER, A. E., and SUSSMAN, W. Practical technique for roentgen pelvimetry with new positioning. AM. J. ROENTGENOL. 81 RAD. THERAPY, 1944, 51, 207-214. . D1EHL, J., and FERNSTROM, I. Radiologic pelvim- etry with special reference to widest trans- verse diameter of pelvic inlet. {Ida radial. (Dias-)1 19661 4) 557—568 . FRIEDMAN, E. A., and TAYLOR, M. B. Modified tomographic aid for x—ray cephalopelvimetry. Am. 7. 051:. (3’ Gyntt., 1969, 105, 1110—1115. . HANNAH, W. J. X-ray pelvimetry—critical ap- Kelly, Madden, Arcarese, Barnett and Brown 16 Senlulu, 1975 praisal. Am. 9'. 05:1. 55 Gymn, 1965, 91, 333- 34°- 9. JOHNSON, T. H., JR., and REAoAN, T. A. Roent- genologic rule and pelvimetry technique. AM. J. ROENTOENOL., RAD. THERAPY & NucLEAR MED., 1969, 105, 890-893. MACMAHON, B. Prenatal x-ray exposure and childhood cancer. 7. Nat. Cancer Inst, 1962, 28, 1173-1191. McGRUDER, C. E. X-ray pelvimetry at teaching hospital: ten year evaluation. :7. Nat. M. A., 1968, 60, 213—214. MURRAY, J. P. Semi-orthometric pelvimetry: appraisal. Brit. 7. Radio]., 1971, 44, 524—530. RUSSELL, J. G. B., and RICHARDs, B. Review of pelvimetry data. Brit. 7. Radial., 1971, 44, 780—784. SCHWARz, G. 5. Radiation hazards to human fetus in present day society. Bull. New York Acad. Med, 1968, 44, 388-399. . SONQUXST, J. A., BAKER, E. L., and MORGAN, J. N. Searching for structure (Alias-Aid-III): approach to analysis of substantial bodies of micro-data and documentation for com- puter program. Institute for social research. The Univ. of Michigan, Ann Arbor, Michigan, 1971. STEWART, A. M., and KNEALE, G. W. Age-dis- tribution of cancers caused by obstetric x-rays and their relevance to cancer latent periods. Lancet, 1970, 2, 4—8. . STEWART, A., WEBB, J., and HEwn'r, D. Survey of childhood malignancies. Brit. M. 7., 1958, 2,1495—1508. . US. Dept. of H.E.W. Health Resources Adm. Final natality statistics 1970, Monthly Vital Statistics 1970 (HRA) 74—1120, vol. 22, 12, p. 6, Io. . US. Dept. of H.E.W. National Center for Health Statistics. Medical x—ray visits and examinations during pregnacy—United States 1963, Public Health Serv. Publication No. 1000, Series 7.2, No. 5, 1968. 10. II. 12. 13. 14. 16. BRITISH MEDICAL JOURNAL 29 NOVEMBER 1975 MEDICAL PRACTICE Occasional Survey Role of pelvimetry in active management of labour D N JOYCE, F GIWA—OSAGIE, G W STEVENSON British Medical Journal, 1975, 4, 505-507 Summary All cases referred for pelvimetry in 1970-1 and all breech presentations referred for pelvimetry in 1972-4 were reviewed. Indications for pelvimetry fell into four main categories: high head in the antenatal clinic (478%); high head in labour (Iii-9%); breech presentation (209%); and previous caesarean section (Ill-8%). In the first two categories pelvimetry rarely if ever influenced manage- ment, and it should not be performed routinely. In breech presentation and cases of caesarean section pelvimetry seemed to be of value, but in the latter group it should be performed puerperally to avoid the known radiation hazard to the fetus. A fairly close correlation between obstetric conjugate and pelvic capacity was shown, which suggested that a 3400-g baby might pass through a pelvis of obstetric conjugate of 10 cm as a cephalic trial of labour, but would need an obstetric conjugate of 11-7 cm for safe vaginal breech delivery. Introduction The work of Stewart et a1“3 has clearly shown that a fetus irradiated in utero runs a greater risk in childhood of developing leukaemia or some other malignancy, a view endorsed by the International Commission on Radiological Protection.‘ Calcula- tions of modern dose levels by Reekie and Davidson“ suggest King's College Hospital, London SE5 1) N 'JOYCE, mu, MRCOG, lecturer in obstetrics (now consultant senior lecturer in obstetrics, South Mead Hospital, Bristol) 17 GIWA—OSAGIE, BM, DRCOG, obstetric senior house officer G W STEVENSON, MRCP, an), senior radiological registrar (now consultant radiologist, Plymouth General Hospital, Devonport) that this risk is about 1 in 30 000 for single obstetric abdomen or erect lateral pelvimetry films. The recognition of this radiation hazard has led many obstetric units to abandon full pelvimetry and to rely on a single erect lateral view in spite of a widespread belief that any single view of the pelvis has little value in predicting the capacity of the pelvis or the outcome‘of labour. Active management of labour with amniotomy and oxytocin administration in slowly progressing labours has been widely adopted in this country after the pioneering work of O’Driscoll et al' 7 and Philpott.” Both groups found that active management led to a striking decrease in the apparent incidence of cephalo— pelvic disproportion, implying that much of what had previously been considered to be disproportion was, in fact, ineflicient labour. Philpott’s group made no attempt at antenatal assess— ment of pelvic capacity, adopting a trial of labour as the universal norm for managing possible disproportion. In the light of these developments we felt it worthwhile to review the place and value of pelvimetry. At King’s College Hospital a policy of active management of labour has been pursued since 1969. Low amniotomy is routinely performed when patients are established in labour and an intravenous oxytocin infusion used if good progress is not maintained as judged by partograms. Continuous fetal heart rate monitoring is used in all high risk cases, with fetal blood sampling when the heart rate is abnormal. Epidural anesthesia is also freely available and in 1974 was used for 33% of all deliveries. Patients and methods We studied all cases in which pelvimetry was performed during 1970 and 1971 and all the breech deliveries for which pelvimetry was performed during 1972, 1973, and 1974. We tried to answer two main questions: (a) what influence did pelvimetry data have on the manage- ment of cases for which is was requested? ([7) What predictive value has erect lateral pelvimetry in cephalic and breech presentation ? The x-ray films were remeasured without reference to the original report or the obstetric outcome until agreement was reached between two of us. The measurements recorded were the obstetric conjugate and the sacral angle. The obstetric conjugate was measured from the Reprinted by permission of The British Medical Association. 17 506 BRITlSH MEDICAL JOURNAL 29 NOVEMBER 1975 [than abttrrri'c conjugates and birthrvrights and method of delivery related In indication for pelt-{merry in 1971-2 - » . . M h t-t ' M M thod {deli -er ". f t'e t- Indlcatton txo ( a.) of cases‘ :flggnfcnc unmet-trig: c o \ y( . o m: n s) (cm) (g) Cacsatean section Forceps Spontaneous High head in antenatal clinic 55 (47-8) 10-88 3273 27-3 34-5 38-2 High head in labour 16 (13-9) 10-86 3199 37-5 25 37-5 Breech presentation 24 (20-9) 12 IR 3230 16-7 70-8? 12-5: Previous caesarean section 17 (14-8) 11-73 3419 29-4 41-2 29-4 'Perccntages are of total group (115), though three patients examined for poor obstetric history have not been included in table. TAssistcd breech delivery. :Spontaneous vertex after \‘crsion. inner edge of the pubic symphysis to the promontary or to the 31—82 '4 ' ' ' . joint if this was nearer. The sacral angle was the angle between the true brim and a line from the sacral promontary to the most prominent part of the front of the first two sacral vertebrae. This angle broadly determines the capacity of the mid-cavity in relation to that of the brim. Results In 1970 and 1971 pelvimetry was performed in 115 cases. In two postpartum cases full pelvimetry was performed, but in the remainder only an erect lateral film was taken. The main indications, the mean pelvic measurements, fetal weights, and the methods of delivery in 112 patients are shown in the table. The remaining three patients were examined because of poor obstetric history. In the 55 patients examined by x rays because of high head in the antenatal clinic all went on to a trial of vaginal delivery, and careful scrutiny of the notes showed no case in which the management would have been any difi'erent if the x—ray films had not been taken. In four cases the pclvimetry film showed the fetal head to be engaged and in several more the head was clinically engaged before the onset of labour. It was more difficult to assess the influence of the x-ray films on the management of the 16 patients examined in labour because of a persisting high head. These patients underwent x—ray examination in the labour ward and five of the 16 films were of insufficient quality to allow measurement of pelvic diameters. In a few cases information of value was obtained—for example, in one case a false promontory was shown, which indicated that the fetal head had much further to go than was clinically apparent. Nevertheless, in most cases the rate of progress was the most important factor determining management. In the breech presentation group pclvimctry seems generally to have been of value. The only two elective caesarean sections in the 1970—1 breech group were done on the only two patients with obstetric conjugates below 11 cm. In the previous caesarean section group there were two elective sections, one in a patient with an obstetric conjugate of 9-9 cm and a previous failed trial of labour for a 4000-g baby, in whom the decision could have been made on clinical grounds, and the other in a patient with a small baby and a well shaped pelvis with an obstetric conjugate of 13-2 cm, in whom the decision was obviously taken in spite of the pclvimctry. In only one of the previous caesarean section cases was pelvimetry performed in the puerpcrium. The relation between obstetric conjugate, birthweight, and mode of delivery in those cases in 1970-1 in which a trial of labour was used 'is shown in fig 1. All the caesarean sections for cephalic presentation are included here except one for placenta praevia and one for brow presentation. The indications for the others were failure to progress or fetal distress or a combination of these factors. The vaginal deliveries are concentrated in the upper left hand side of the diagram and lines have been drawn which empirically define zones where nil, 50"“, and 90?}, of the women delivered vaginally. From January 1970 to December 1974 there were 89 breech deliveries in patients who had had pelvimetry performed antenatally. There were five hydrocephalics which were excluded from further consideration. Of the remainder 56 delivered vaginally, 10 had elective cacsarean sections, and 18 had caesarean sections during labour. The indications for the caesarcan sections in labour were: failure to progress 11 cases, fetal distress four cases, and cord prolapse three cases. Apart from the hydrocephalics there was only one death in the total group. This was a 3820—g fetus delivered as an assisted breech without undue difficulty through a 12-2 cm obstetric conjugate pelvis. The baby collapsed and died two days after delivery and necropsy showed a subarachnoid hacmorrhagc. There was no record of any significant trauma in any other case. The relation between birthwcight and obstetric conjugate and method of delivery for these breech deliveries is shown in fig 2. Failed vaginal delivery included all the caesarcan sections in labour except 'l8 Obstetric conjugate (cml 2500 3000 3560 who 4530 Birthweith (9) FIG l—Relation between obstetric conjugate, birth weight, and outcome of labour in trial of labour with cephalic presentation 1970-1. 0 = Vaginal delivery. 0 = Caesarean section for failed trial of labour. Obstetric conjugate (cm) 9 - 2500 3600 35'00 4000 4500 Birthweiqht (q) no Z—Rclation between obstetric conjugate, birth- wcight, and outcome of labour for breech presentation 1970—4. 0 * Vaginal delivery. 0 = Failed vaginal delivery. E — Elective cacsarean section. 7 = Neonatal death after vaginal delivery. the three for cord prolapse. A line parallel to those in fig 1 can be drawn which separates most of the failed vaginal deliveries from the successful vaginal deliveries. This line is the equivalent of 1-8 cm 0‘ nmrisn MEDICAL JOURNAL 29 NOVEMBER 1975 obstetric conjugate higher than the bottom line of the trial of labour chart and 1-3 cm higher than the top line. Apart from elective caesarean section and cord prolapse the indications for the ceasarean sections which fell above this line were fetal distress (1) and failure to progress (2). Indications for those below the line were fetal distress (3) and failure to progress (9). There was one successful vaginal delivery which fell off the chart and below the line. This was a Cushingoid prediabetic baby weighing 4585 g who was delivered through a pelvis with an obstetric conjugate of 12] cm. This baby had a head circumferance of only 34 cm, a measurement which is the mean for a weight of 3150 kg. Such a birthweight would have fallen well above the line. We found no significant correlation between sacral angle and out- come of labour in either cephalic or breech presentations. Discussion We were surprised to find such a clear correlation for both cephalic and breech presentation between obstetric conjugate and the size of fetus that could deliver vaginally. The active management of labour has probably eliminated much of the uncertainty in labours associated with poor uterine action, in which disproportion was often assumed to be present. It is also possible that our obstetric population has more uniformity of pelvic shape than was the case 20 or 30 years ago in the “golden age of pelvimetry," when some women had pelves distorted by rickets. The higher cut-off line in breech presentation is in keeping with traditional obstetric teaching, and with the Peri— natal Mortality Survey findings of minimal breech mortality in birthweight groups below 3175 g (7 1b). Our data suggest that for the average breech at term (weight 3400 g) a minimum obstetric conjugate of 11-7 cm would be necessary for safe vaginal delivery, and for the average breech at 38 weeks (weight 3200 g) an obstetric conjugate of 11-4 cm would be necessary. The value of pelvimetry in predicting the outcome of labour is limited by the difficulties of assessing fetal weight, though there is a fairly close correlation between fetal weight and biparietal diameter measured by ultrasound. From the data of Campbell” biparietal diameters corresponding to 2500, 3000, 3500, and 4000 g are 88, 94, 101, and 108 mm respectively. Despite the reasonable correlation with outcome antenatal 507 pelvimetry is rarely justified except in breech presentation. With a breech the size of pelvis that is needed for an average-sized baby is beyond the reach of accurate clinical assessment. The known risks to the fetus of difficult breech delivery easily outweigh the radiation hazard. On the other hand, with a cephalic presentation an average—sized baby can be expected to pass through a pelvis which is detectably small on clinical assessment. Furthermore, there is no evidence that a failed trial oflabour entails any significant risk to the fetus. In a primigravida an elective caesarean section for disproportion is only likely to be indicated when the pelvis is distorted by bony disease or fracture. In patients with a previous caesarean section or poor obstetric history pelvimetry may influence the management of the case but should generally be performed in the puerperiun. rather than during the next pregnancy. With twins there is no appreciably greater risk for breech presentations, as the babies tend to be both premature and small for dates. Pelvimetry for twins is only likely [to be of value in patients with a clinically suspected contracted pelvis. In summary, routine pelvimetry should be performed only in the following cases: (a) antenatally, for singleton breech presentations in primigravid and multigravid patients; (b) postpartum, after a caesarean section, difficult forceps delivery, or perinatal death, when vaginal delivery might be considered in a subsequent pregnancy; (c) before pregnancy, after the healing ofa fractured pelvis or at some suitable point in the management of other relevant orthopaedic disorders. References ‘ Stewart, A M, er al, Lancet, 1956, 2, 447. ’ Stewart, A M, Webb,] W, and Hewitt, 1), British Medicalj'oumal, 1958, 1, 1495. ’ Stewart, A M, and Kneale, G W, Lanrel, 1968, 1, 104. ‘ International Commission on Radiological Protection, Health I’lzyricr, 1966,12, 291. "' Reekie, D, and Davidson,] K, British Journal of Radiology, 1967, 40, 849. ‘ O‘Driscoll, K, Jackson, R] A, and Gallagher,] T, British Alcdimljournal, 1969, 2, 477. 7 O’Driscoll, K, Jackson, R J A, and Gallagher, J T,]oumal of Obstetrics and Gynaecology of the British Commonwealth, 1970, 77, 385. " Philpott, R H, British .H’edical journal, 1972, 4, 163. ‘ Campbell, S, Clinic: in Obstetrics and Gynaecology, 1974, 1, 55. 19 5l4 JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION NOVEMBER, 1976 X-ray Pelvimetry: Useful Procedure or Medical Nonsense J. A. CAMPBELL, M.D., Marlin Luther King Hospi/al, Lo: Angeler, Cali/omit”; PHYSICIANS are becoming increasingly aware of the growing problem of over utilization of radiologic and laboratory procedures. The proliferation of these is one of the major causes of the upward spi- ral of medical patient costs by requiring larger investments in equipment, supplies and personnel. Unproductive radiologic examinations waste manpower and de- crease the efficiency of patient care deliv- ery. The causes of the over utilization of diagnostic procedures are numerous. These include insurance indemnification, fear of malpractice suits, training of physicians by protocol, and the rationalization by clini- cians and radiologists of the usefulness of traditional procedures or those which du- plicate other findings. Control of the over utilization of exami— nations requires agreement by clinicians and radiologists on the worthiness of any given procedure based on a medical audit of its effectiveness. If the present escalation of costs continues, we can look to a time when economic factors may necessitate that licensure or accreditation of physicians be linked to the positive yield of their diagnos- tic laboratory examinations in a manner similar to the College of Surgery’s accredi- tation of surgeries on the basis of the per- centage of operations yielding pathology. In certain Canadian Provincial health care systems, payments of insurance benefits to attending physicians, clinicians and radiol- ogists alike, are discounted when the an- nual yield of their diagnostic procedures exceeds the percentage of the normal pre- scribed by auditing standards. No definitive harm to patients from di- agnostic radiography has been validated. There is a steady annual increase in the number of such examinations. The fact that the majority of such studies show normal findings, and that a greater number of healthy persons are exposed by screening programs causes some public health agen- cies to be concerned about the risk-benefit ratio of these diagnostic procedures. THE PROBLEM In recent years, ultrasonic technics, where available, have largely replaced ra— diographic examinations in obstetrical di- agnosis. Pelvimetry remains the major source of ionizing radiation to the fetus. Understandably, radiologists and obstetri- cians differ in their attitudes toward the usefulness of pelvimetry. Radiologists are chiefly concerned with the discovery of fe- tal, uterine, and placental abnormalities and having a growing distrust of pelvimetry as a valid method of determining true ceph- alopelvic disproportion. Obstetricians have become more aggressive in their manage- ment of labor with an increased use of in- duction and caesarean section, and there- fore view pelvimetry as an aid in avoiding the theoretical risk of birth injury during vaginal delivery through an abnormal pel- vis. To adjust for these philosophical dif- ferences, some radiologists have modified their pelvimetry technics to include an im- age of the entire uterine contour in the anteroposterior and erect lateral views in order to improve detection of fetal abnor- malities. It often appears that obstetricians utilize pelvimetry as a means of reassuring themselves that the pelvic measurements are normal in much the same way as a blood count or urinalysis is used to exclude ane- mia or diabetes. The question raised by radiologists is whether pelvimetry is accu- rate enough in sorting out those cases which Reprinted from tEe Journal of The National Medical Association, November 1976, Vol. 68, No. 6, pp. 514-520. Copyright 1976 by The National Medical Association. (Reprinted by permission of The National Medical Association) 20 Vol. 68, No. 6 X-ray Pelvimetry 515 are at risk in vaginal delivery to justify its use. It is easy to find statistical evidence to support their skepticism. For example, from April 1972 to April 1976, there were 8235 infants born at MLK Hospital in Los Angeles with 90% of these delivered vaginally (caesarean section rate of 10% ). Approximately 17% of these cases had x—ray pelvimetry. The radiologic yield of these 1377 pelvimetries is as follows: Table 1. RADIOLOGIC YIELD OF PELVIMETRY-MLKH Absolute cephalopelvic disproportion 1 Low normal measurements 42 Normal pelvimetry 1334 Two cases of obvious disproportion due to hydrocephalus were excluded‘ from this series. These pelvimetry studies also revealed the following conditions which might cause complications at delivery (Table 2). Table 2. ANCILLARY YIELD OF PELVIMETRY MLKH Breech presentations 88 Face presentations 4 Transverse presentations 19 Twin fetuses 45 Placenta previa 41 Felal anomalies Fetal demise 4 Pelvic deformity It should be pointed out that most of these diagnoses could be made by means other than radiography (Ultrasound, etc.). Interestingly, in none of the cases show- ing traumatic deformities of the pelvis was there sufficient contraction of the birth canal to cause dystocia. The incidence of absolute disproportion coincided with the rates of one to two cases per 2500 pelvime- tries expressed in other series.1 Assuming an 21 overall cost of $50.00 per case, this rate requires the expenditure of $60,000 for each case of cephalopelvic disproportion discovered by pelvimetry. Obstetricians may justifiably reason that this cost is far less than the lifetime care of a child rendered spastic by birth injury, however. To appraise the attitudes of other radiol- ogists regarding the usefulness of pelvime- try, 40 teaching centers were surveyed with the following results (Table 3). Table 3. RESPONSE OF RADIOLOGISTS‘ SURVEY ON THE USEFULNESS OF X-RAY PELVIMETRY 1. Yield justifies its clinical use 35% 2. Yield does not justify its clinical use 65% 3. Is not indicated as a routine procedure 82% 4. Performed on judgment of obstetrician 22% 5. Is justified only in the following: a) Failure of progress of labor 40% b) Persistent breech presentation 25% 0) Prior to induction of labor 32% d) History of pelvic trauma [0% Obviously, there is a two-way bias re- garding pelvimetry. What are the factors which enter into this dichotomy of thought? One has only to consider the size of a fetal skull and the pelvis of the mother to ap- preciate that the passage of one through the other leaves little room to spare. It is there- fore logical to assume that the determina- tion of the skull and pelvic diameters will permit a forecast of the course of labor. For many years, obstetricians and radiologists have clung to this belief despite mounting evidence to the contrary. Theoretically at least, pelvimetry is an attempt to discover that tiny minority of women with very small or contracted pelves who are certainly likely to have obstructive difficulty in delivering a fetus vaginally. Pelvimetry is only one of many factors which influence the prognosis of vaginal delivery. The problem is to as- certain what pelvimetry measurements, if any, and discounting other influences, pre- clude trouble-free passage of the fetal head through the pelvis. 516 JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION NOVEMBER. 1976 FACTORS INVOLVED IN THE CLINICAL BIAS It is the obstetrician who chiefly governs the indications for pelvimetry. He selects, by clinical assessment, the woman whom he suspects has a small pelvis. This process is diflicult and highly imperfect. Russell and Richards2 compared the pelvic sizes of women referred for'pelvimetry with those of a control group and revealed only small, differences in the two groups. The pelvime- try patients showed 6% with at least one measurement smaller by 2 standard devia- tions than the mean. In the control group, this figure was also 6%. The caesarean sec— tion rate for the pelvimetry group was 29%. while the section rate for all patients in the hospital for the sameperiod was 8.1%. It was noted that this high section rate oc- curred even in patients with average or larger than average pelvic measurements. Similarly, these authors noted that the forceps rate for women with cephalic vagi- nal deliveries was 23%, more than four times the average for those with similar ver- tex deliveries who did not have pelvimetry. It would appear that the obstetricians in this series were chiefly selecting for radio- logic pelvimetry those patients who were going to have difficulty in labor rather than those with small pelves. Russell2 felt that in the large majority of referrals, pelvic size was not the important factor, nor was fetal size, because he found no difference in the birth weight between pelvimetry patients and those of the normal hospital popula- tion. From this study, this author concluded that the factor causing referral is likely to be tightness or poor relaxation of the soft tissues which make digital pelvic assessment difficult and give rise to soft tissue dystocia with poor pelvic molding. Pelvimetry is of no help in evaluating this factor. This evi- dence would support the thesis that the bony pelvis is responsible for dystocia in only a very small minority of cases. Thus it. would appear that in considering patients for pelvimetry there is need for a more accurate clinical assessment of pelvic size 22 in an effort to identify the larger group of dystocic patients who have normal pelvic size. The radiologists surveyed often ex- pressed the opinion that younger obstetri- cians order normal pelvimetries more fre- quently than their more experienced col- leagues, probably reflecting their insecurity in clinical assessment of the patient. In many institutions, residents in obstetrics are taught to request pelvimetry by protocol, rather than by clinical decision. It seems reasonable to insist that pelvimetry be car- ried out only after clinical assessment by a senior obstetrician if over-utilization of this examination is to be curbed. Clinicians can assess the ability of the fetal head to enter the pelvic inlet as a meas- ure of disproportion, but they should not conclude that the head “won’t push in" un- less the patient has been examined while standing. Frequently, when such patients are referred for pelvimetry, the erect lateral film shows the head to be easily engaged. Because the engagement of the head is often delayed in the teenage mother, fear of disproportion may arise. Mussioa showed that there is little change in the size and shape of the pelvis after puberty, and any growth is completed within a year. Thus the incidence of cephalopelvic disproportion is not increased in adolescence, and youth in itself is not an indication for pelvimetry. A persistent breech presentation in a primip does need careful clinical consideration. It should be poined out, however, that per- sistence of the breech position usually oc- curs in women with a large, not a small pel- vic inlet, which more readily accommodates the breech. Thus the probability is that the transverse inlet diameter is usually wider than normal in such presentations. Todd and Steer4 found in a review of 1006 breech deliveries that a sagittal inlet of 11.0 cm (which can be estimated by vaginal exami- nation), allowed safe vaginal delivery; Since molding of the fetal head is chiefly caused by uterine pressures, not the bony pelvis, the diameter of the head is capable of about as much reduction in diameter in breech as with vertex deliveries. Vol, 68. No. 6 X-ray Pelvimelry 5l7 Another interesting observation in our series was the 80% incidence of definite diastasis of the symphysis pubis in cases of breech presentation even when the fetal pel- vis was not engaged in the inlet. This find— ing is further evidence that pelvic molding is not necessarily the result of mechanical intrapelvic forces. A small group of women needing special attention are those with a history of trauma or other deforming dis— ease affecting the pelvis. A review of pre- vious pelvic films during prenatal care is most valuable in deciding if pelvimetry is needed. An obstetrician, with a “favorite" meas- urement associated with difficult vaginal de- livery, is strongly biased toward interference with the natural labor of a woman in whom he knows this measurement to be outside of his normal limit. However, retrospective analyses (by Borell and Fernstrom”) made on data which were not used to prove the specific value of some measurement, failed to justify such a correlation. In line with this. Russell“ points out that, if a small pelvis is defined as one with a measurement associated with an increased rate of for- ceps delivery, 4% of women who had pel- vimetry have a small pelvis. However, 2% of women who did not have pelvimetry, have a small pelvis similarly defined. Our series showed even less difference in the rate of low forceps deliveries between the pelvimetry and non-pelvimetry groups. FACTORS INVOLVED IN THE RADIOLOGIC BIAS There are several important factors which significantly offset the precision of pelvimetry measurements as an indicator of dystocia. The first of these is the reshaping of the fetal head diameters during labor as a result of molding. Head molding is most marked when the head is above the outlet. In the great majority of instances, the bony pelvis is large enough to transmit the un— molded head. Lindgren7 pointed out that molding of the head is a response to soft tissue pressure. The fact that head molding is not infrequently seen in breech presen- 23 tations would suggest that the uterine mus- culature forcibly pushes the uppermost part of the fetus downward. Molding of the head is capable of reducing the biparietal and occipitofrontal diameters by more than 1 cm. Evaluation of the fetal skull area or volume in relationship to the pelvic size was made by King, who found no convinc- ing evidence that this approach added to the accuracy of predicting dystocia. A second factor, often not fully appre- ciated, is molding of the maternal pelvis which produces alterations in its dimen- sions. GrahamS noted that even in the Hip- pocratic era, it was assumed that the pelvis expanded during delivery. This was first thought to be a simple diastasis of the sym- physis pubis, but later recognized that as the pressures separated the ischial spines, Fig. 1. Pelvic Molding in Vertex Presentation. There is wide separation of the symphysis pubis, even though the fetal head is high in the pelvis. ' the iliac crests moved inwards to produce a rocking motion of the symphysis, effecting its separation. The sacroiliac is a synovial type of joint capable of considerable mo— tion in both males and females, but these are greatly increased in pregnancy. Sacro- iliac motion is either sliding or rotatory in character relative to the pelvis girdle. These motions are visible on successive lateral radiographs of the pelvis on a subject ex- posed in different postures. Movements of the legs and trunk cause sacroiliac motion depending on the stresses exerted such as the asymmetrical one commonly observed in walking. These rotary or sliding move- ments of the sacroiliac joints alter the coro— nal and sagittal diameters of the pelvis. 518 During pregnancy, the iliac crests move in- ward or outward causing separation of the ischial spines and the symphysis. This sep- aration is considerably greater than the actual movement of the sacroiliac because of the principle of levers (Figs. 1 and 2). Fig. 2. Pelvic Molding in Breech Presentation. The symphysis pubis is widely separated even though the fetal breech lies in the pelvic inlet. Evidence of these forces acting on the symphysis is the visibility of gas in the sym- physis pubis. This is due to the “vacuum phenomenon” seen when a joint is forcibly separated. On the anteroposterior film, gas is seen in the symphysis in over 50% of pregnancies at term. It tends to localize in the upper part of the joint in recumbency and in the lower part of the joint when films are taken in the erect position, reflecting the variation in the mechanism of abstrac- tion (Figs. 3 and 4). Borell and Fernstrtim5 measured the mag- nitude of pelvis molding in pregnant women radiologically and found that the sagittal outlet diameter increased from 1 to 2 cm in changing from a decubitus to a standing position. Russelllo noted an increase in the bispinous diameter of up to 1.6 cm between a supine and semi-squatting position where the abducted femora and flexed knees act as levers to force the outlet open. This was probably the greatest benefit derived from the use of the old fashioned birth stool. Thus, in some women, depending upon the shape of their sacroiliac joints and laxity of their soft tissues, a simple postural change can increase the sagittal diameter of the JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION 24 NOVEMBER, 1976 outlet by as much as 2 cm and the transverse diameter by 1 cm or an increase of 30% in area. With these changes in the pelvic shape, the outlet area is further enlarged by the increase in the sub-pubic angle. Fur— thermore, it is very probable that far more molding of the pelvis occurs at delivery than that observed antenatally with these changes in posture. From this evidence, it appears that more dilatation of the pelvic outlet could be achieved through the natural lev- erage of the femora than by pulling the head through the outlet with forceps. Fig. 3. Gas in Symphysis Pubis. Note that the gas due to the vacuum effect of the separated symphysis lies only in the upper half of the joint as a result of the wedging of the pubic bones by the pelvic molding with the patient in the supine decubitus posture. It is obvious that the degree of pelvic molding depends on the mother’s position at the time of delivery. Likewise, the di- ameters measured on pelvimetry vary con- siderably between the erect and decubitus positioning of the patient. Consequently, the obstetrician should be aware of the posture in which the measurements were made. In visiting more than one hospital or radiology office where different positions are used for pelvimetry, he should make appropriate ad— justment for the differing normal limits per- taining to the variations in the technic used. In cases with borderline measurements, it is' particularly important that a radiologic as- sessment of the magnitude of the sacro- symphysis molding of the pelvis be made in order to properly discount the pelvimetry values obtained. The criteria for the pelvic outlet meas- urements which permit a trouble free de- Vol. 68, No. 6 X -ray Pelvimetry 519 livery are much less reliable than those for the inlet because the effects of pelvic mold- ing on the inlet diameters are less pro- nounced. Certain formulas concerning out- let measurements can therefore be mislead- ing to the obstetrician. It is frequently taught that outlet dystocia may be anticipated if the sum of the sagittal outlet (distance from lower edge of symphysis to the distal tip of the sacrum) and the intertuberous diame- ters is less than 24 cm. Russell and Rich- Fig. 4. Gas in Symphysis Pubis. In this case. the vacuum phenomena has produced gas in the lower portion of the symphysis area as a result of diastasis of the joint occurring with the patient in the erect posture. ards2 found, that the forceps rate for all vertex deliveries in patients with combined measurements of the bituberous and sagittal outlet of 24 cm or more was no different than for all those with less than 24 cm. The Colcher-Sussman technic‘1 prescribes that the sum of the sagittal distance from the ischial tuberosities to the sacral tip and the bituberous diameter should be 16 cm or greater to avoid outlet dystocia. Evalua- tion of our pelvimetries shows no increase of the forceps rate in those cases with measurements below 16 cm, however. COMMENT For the radiologist to present the limita- tions of pelvimetry to an obstetrician is like sitting down with your mother-in-law to discuss her faults. The two-way bias is un- derstandably based on the fact that the ra- diologist is concerned with the lack of ac- ceptable yield from pelvimetry, whereas the 25 obstetrician utilizes the procedure to survey patients whom he suspects may have trouble in vaginal delivery and not necessarily those suspected of having a small pelvis. Correlations between pelvic measure- ments and the course of labor are quite un- satisfactory-from a statistical point of view. When an analysis made retrospectively on data which have not been obtained to prove the value of a measurement, positive cor- relation seems to vanish. It cannot be dis- puted that pelvimetry can identify that tiny minority of women with significantly small pelves. These are usually defined as one in which the bispinous diameter is less than 9 cm or the symphysis—sacral sagittal di- ameter of the outlet is 10 cm or less, and these patients are certainly more likely to have obstructive difficulties in labor. But the incidence of a truly “small” pelvis in patients selected for pelvimetry is frequently as low as one or two cases in 2500. In addition, the effects of molding of the fetal head and maternal pelvis during labor may expand these diameters sufficiently to (2-3 cms) render them meaningless. It is clear that attempts to forecast the outcome of labor in cases where the pelvic size is low average, average, or above aver- age are doomed to failure because the caesarean and forceps rates in patients who have had pelvimetry and have adequate measurements are very high. CONCLUSIONS There are numerous factors which ad- versely effect the progress of labor, and the contracted bony pelvis is statistically among the least of these. This fact, coupled with the evidence that head and pelvic changes during parturition frequently offset the pre- cision of the findings, casts significant doubt on the usefulness of pelvimetry with its attendant radiation exposure. No increase in birth injury has so far been reported on services where pelvimetry has been largely discarded, but this type of control study should be researched in the future. At the very least, certain guidelines in the use of pelvimetry seem warranted to reduce its 520 JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION NOVEMBER, 1976 overutilization. The following suggestions are offered. 1. Select patients on the basis of iridi- vidual clinical assessment, not by protocol. 2. Other causes for failure of progress of labor should be excluded, by other meth— ods when possible, prior to pelvimetry. 3. The possibility of inlet dystocia should be assessed clinically or by ultrasound methods, with the patient erect, prior to employing pelvimetry. 4. Dystocia due to fetal anomalies, pla- centa previa, multiple pregnancy, and fetal demise can usually be diagnosed by ultra- sound without resort to pelvimetry. 5. The magnitude of pelvic molding should be assessed in all cases with low pelvimetry measurements. 6. The significance of pelvic deformi- ties can be assessed on prior films without resort to pelvimetry. 7. Induction of labor is not in itself an indication for pelvimetry. 8. Breech presentation is not in itself an indication for pelvimetry. 9. Youth (adolescence) is not in itself an indication for pelvimetry. LITERATURE CITED 1. Quoted by SANDERS, R. C. on experience at 26 10. 11. Johns Hopkins Hospital, Baltimore, Md., 1976. RUSSELL, J. G. B. and B. RICHARDS. A Re- view of Pelvimetry Data. Brit. J. Radiol., 44:780-784, 1971. Mussto, T. J. Primigravidas Under Fourteen. Am. Jour. Obstet. Gynecol., 84:442-444, 1962. . TODD, W. D. and C. M. STEER. Term Breech: A Review of 1,006 Term Breech Deliveries. Obstet. Gynecol., 22:583-595. BORELL, U. and K. FERNSTROM. Radiologic Pelvimetry. Acta Radiologica, Supplement, 19] : 1960. RUSSELL, J. G. B. Radiology in Obstetrics and Antenatal Pediatrics, Radiology in Clini- cal Diagnosis Series, Buttcrworth and Co. Ltd., London, 1973. LINDGREN, L. The lower Part of the Uterus During the First Stage of Labor in the Oc- cipitoanterior Vertex Presentation. Acta Ob- stetrica et Gynecologica, 34: Supplement 2, 1955. GRAHAM, H. Quoted by Eternal Eve, London, Heinemann, 49, 1950. BORELL, U. and K. FERNSTROM. The Move- ments at the Sacroiliac Joints and Their Im- portance to Changes in the Pelvic Dimensions During Parturition. Acta Obstetrica ct Gyne- cologica, 36:42-57, 1957. RUSSELL, J. G. B. Moulding of the Pelvic Outlet. J. Obstet. Gynecol. Brit. Common- wealth, 76:817-820, 1969. COLCHER, A. E. and W. SUSSMAN. Practical Technique for Roentgen Pelvimetry with New Positioning. Am. J. Roentgenol., 51: 207, 1944. a U. S. GOVERNMENT PRINTWG OFFICE : 1980 628-930/2757 FDA 79-8088 FDA 79-8090 FDA 79-8093 FDA 79—8094 FDA 79-8097 FDA 79—8098 FDA 80-8024 FDA 80-8027 FDA 80-8034 FDA 80—8057 FDA 80-8070 FDA 80-8092 FDA 80-8095 FDA 80-8096 FDA 80-8100 FDA 80-8101 FDA 80-8102 FDA 80—8103 FDA 80-8101l FDA 80—8105 FDA 80-8106 FDA 80—8107 FDA 80-8108 FDA 80—8109 FDA 80-8110 FDA 80-8116 FDA 80-8117 FDA 80-8118 FDA 80-8119 FDA 80-8120 FDA 80-8123 FDA 80-8124 FDA 80-8127 X Rays: Get the Picture on Protection (brochure). Source Book of Educational Materials for Radiation Therapy (GPO 017-015-00159- 8, $4.50) (PB 299 415/AS, rnf only). Guide for the Preparation of Cathode Ray Tube Reports Pursuant to 1002.10 and 1002.12. Quality Assurance for Radiographic X—Ray Units and Associated Equipment (PB 80— 101 405, $9.00). Analysis of Retakes: Understanding, Managing, and Using an Analysis of Retakes Program for Quality Assurance (PB 80-102405, $6.00). Bureau of Radiological Health Index to Selected Acoustic and Related References (PB 80—120967, $20.00). FDA X-Ray Record Card (card). Directory of Personnel Responsible for Radiological Health Programs (supersedes FDA 80-8027, September 1979). Report of State and Local Radiological Health Programs, Fiscal Year 1978 (PB 80- 130867, $6.00). Nationwide Evaluation of X-Ray Trends: (supersedes FDA 78-8057). Bureau of Radiological Health Publications Subject Index (supersedes FDA 80- 8070, October 1979). Biological Bases for and Other Aspects of a Performance Standard for Laser Products (PB 80-1286‘48, $6.00). Quality Assurance for Fluoroscopic X-Ray Units and Associated Equipment (PB 80- 129778, $8.00). guality Assurance for Conventional Tomographic X—Ray Units (PB 80-128838, 7.00 . Implementation of a Quality Assurance Program for Ultrasound B-Scanners (PB 80- 138340, $6.00). Ionization Chamber Smoke Detector Meeting (PB 80-128705, $7.00). Inexpensive Microwave Survey Instruments: An Evaluation (PB 80-1 M028, $5.00). Analysis of Some Laser Light Show Effects for Classification Purposes (PB 80- 131576, $5.00). The Selection of Patients for X-Ray Examinations (GPO 017-012-00285-4, $3.50) (PB 80—157431, mf only). X Rays: So You Want To Be In Pictures? (Bookmark). An Evaluation of Microwave Emissions from Sensormatic Electronic Security Systems (PB 80-155385, $5.00). Quantitative Analysis of the Reduction in Organ Dose in Diagnostic Radiology by Means of Entrance Exposure Guidelines (GPO 017-015-00164—4, $1.75) (PB 80- 174956, mf only). Positive Beam Limitation Effectiveness Evaluation (GPO 017-015-00163—6, $2.00) (PB 80-166937, mf only). Proceedings of a Workshop on Thermal Physiology (PB 80-187867, $8.00). Quality Assurance Programs for Diagnostic Radiology Facilities (GPO 017—015— 00166-1, $2.50) (PB 80—183338, mf only). Chest X—Ray Screening Practices: An Annotated Bibliography (GPO 017-015- 00167-9, $3.50) (PB 80—183890, mf only). X Radiation and the Human Fetus - A Bibliography (PB 80-157712, $15.00). A Word of Caution on Tanning Booths (brochure). Measurements of Emission Levels During Microwave and Shortwave Diathermy Treatments (GPO 017—015-00168—7, $1.75) (PB 80-194772, mf only). Microwave Oven Radiation (brochure) (supersedes FDA 79-8058). Guide for the Filing of Annual Reports for X-Ray Components and Systems. Optimization of Chest Radiography - Proceedings of a Symposium Held in Madison, Wisconsin, April 30-May 2, 1979. Guide for the Filing of Annual Reports (21 CFR Subchapter 3, Section 1002.11). Dental X—Ray Data (brochure) I .'I US DEPARTMENT OF THIRD CLASS BULK RATE HEALTH AND HUMAN SERVICES POstage Fees Paid Public Health Service PHS Food and Drug Administration pERMIT (529 Bureau of Padiological Health Rockviile, Maryland 20857 Wpuolmiafifl ; OFFICIAL BUSINESS ADDRESS CORROECTION REQUESTED R th hee aibov aredd you do NOT wish to eithis sma iall [3 or if change of addc: eede etdE] (i ni-d t h g nclu din ng aslesPnc bed I smog-(m) unimulwoxg .fizn‘awwad. an u _ W “ f «su9 ; wwxgfimx loge}; "”"7 I n. I I II I I‘ I , ‘ ‘H‘l ' E II ' 'I‘ I i I II: I I I , I “g I ; ‘ M .I f IIIIII' I |ImI I i I .III‘ I II HHS Public ado 0(n (FDA) so 8123 . :9 ' AN EQUAL OPPORTUNITY EMPLOYER 7:3; I GENERAL UBRARY-ILC.BERKELEY lflm‘llillflllllllfll BDDUSDSLLS ETURN PUBLIC HEALTH LIBRARY 42 Warren Ho|| 642-2511