key: cord-0850288-zz7n7fbq
authors: Eid, Joe; Stahl, David; Costantine, Maged M.; Rood, Kara M.
title: Oxygen saturation in pregnant individuals with COVID-19: Time for re-appraisal?
date: 2021-12-16
journal: Am J Obstet Gynecol
DOI: 10.1016/j.ajog.2021.12.023
sha: 50455cd462e9b4ca184445cbe09676235b7d053f
doc_id: 850288
cord_uid: zz7n7fbq

Managing pregnant individuals with acute respiratory disease secondary to Coronavirus disease 2019 has been a challenge. Most professional societies including the Society for Maternal Fetal Medicine recommend keeping oxygen saturation greater than or equal to 95% in pregnant individuals. Reaching this target has been increasingly difficult in some patients, especially with the latest wave of the virus attributed to the delta variant. In the absence of strong data, and in the setting of reassuring fetal status, we propose maintaining maternal oxygen saturation between 92-96% for admitted patients with acute respiratory failure requiring supplemental oxygen. This may prevent unnecessary invasive interventions that might not be of maternal or fetal benefit, specifically at very preterm gestational ages.

Managing pregnant individuals with acute respiratory disease secondary to Coronavirus disease 23 2019 has been a challenge. Most professional societies including the Society for Maternal Fetal 24

Medicine recommend keeping oxygen saturation greater than or equal to 95% in pregnant 25 individuals. Reaching this target has been increasingly difficult in some patients, especially with 26 the latest wave of the virus attributed to the delta variant. In the absence of strong data, and in the 27 setting of reassuring fetal status, we propose maintaining maternal oxygen saturation between 28 92-96% for admitted patients with acute respiratory failure requiring supplemental oxygen. This 29 may prevent unnecessary invasive interventions that might not be of maternal or fetal benefit, 30 specifically at very preterm gestational ages. 31

During pregnancy, several professional societies recommend maintaining oxygen 46 saturation (SpO2) at 95% or greater. 1, 2, 3 In response to the current Coronavirus disease 47 consider targeting an oxygen saturation that is higher in pregnant individuals with severe acute 49 respiratory syndrome coronavirus 2 (SARS-CoV-2) than would be recommended for non-50 pregnant population (SpO2≥92%). Furthermore, they recommend consideration for inpatient 51 monitoring of pregnant individuals with moderate or severe signs/symptoms of COVID-19 and 52 those with SpO2 below 95% on room air with exertion. These patients should call their 53 healthcare provider, undergo prompt evaluation, and be considered for inpatient admission, as 54 94% and this is based on known physiologic changes in pregnancy such as increase in partial 67 maintaining a SpO2 ≥ 95% 3,6,7 cite a paper published by Bhatia et. al. 8 These authors state that a 69 partial pressure of oxygen (PaO2) of 70 mmHg is required to maintain adequate fetal 70 oxygenation, which they also associate with a maternal SpO2 of 95%. 8 if they were intubated and within 7 days of delivery, and used the birth outcome of "perinatal 75 asphyxia" compared to historical data to suggest a causal mechanism of neonatal hypoxia. 9 76

Applying this data to modern guidelines ignores the more than 20 years of progress that has been 77 made in the management of ARDS as well as confounding conditions such as the high rate of 78 maternal multisystem organ failure. While evidence from severe acute respiratory syndrome 79 (SARS) and COVID-19, have suggested a higher rate of fetal growth restriction in cases of 80 severe maternal illness, 10, 11, 12 this is likely multifactorial rather than limited to hypoxemia. There 81 is no compelling objective evidence that a SpO2 of 95% is required for adequate fetal 82 oxygenation. 83

Mallampali et al., recommend maintaining the maternal PaO2 greater than 60-70 mmHg 84 to avoid adverse effects on uteroplacental perfusion. 13 Whereas other experts suggest that a PaO2 85 above 60 mmHg (correlating with SpO2 above 90%) is a reasonable target in pregnant 86 individuals with acute respiratory failure. 12,14 This is due to fetal hemoglobin having a higher 87 affinity for oxygen than adult hemoglobin making the fetus more resistant to changes in maternal 88 oxygen saturation and some degree of hypoxia. 15,16 A PaO2 of 60 mmHg was also supported as 89 being adequate for fetal oxygen delivery based on data from pregnant individuals living at high were associated with increased risk of maternal morbidity, the use of SpO2 <95% was not 97 (relative risk RR 1.3, 95% CI 0.2-7.9). 19 Shields et al. published a maternal early warning tool 98 using different cutoffs for SpO2. They used a SpO2 less than 90% as a single severe parameter 99 and a SpO2 less than 93% as a non-severe parameter. However, low oxygen saturation (whether 100 <90 or <93) was a rare occurrence, seen in less than 0.1% of included patients. 20 In conclusion, 101 the paucity of clinical data and lack of significance seen in early warning models do not provide 102 strong evidence to support using a SpO2 ≥ 95% as a cutoff in pregnant individuals presenting 103 with acute respiratory distress. 104 105 Challenges in maintaining a SpO2 ≥ 95% 106

In non-pregnant individuals with acute respiratory failure secondary to COVID-19, current 107 guidelines recommend starting supplemental oxygen when levels drop below a SpO2 of 90% 108 (strong recommendation, moderate quality evidence) and suggest its use when SpO2 falls below 109 92% (weak recommendation, low quality evidence oxygen therapy should be titrated to avoid SpO2 levels above 96%. 5 Using a minimum target of 116 95% for oxygen saturation in pregnancy would make it more difficult to titrate oxygen 117 supplementation in order to avoid SpO2>96%. 118

When COVID-19 progresses to ARDS, there is a paucity of data to guide oxygen goals. Fetal oxygenation depends on maternal oxygenation and placental perfusion. Significant 158 disturbances to maternal oxygenation may lead to fetal hypoxia which is often reflected as a non-159 an indicator of fetal wellbeing and having a reassuring fetal heart rate is associated with adequate 161 oxygenation and perfusion of the fetus. 37,38 Fetal heart rate monitoring can be used as an 162 additional "vital sign" that may help manage the maternal condition and guide the decision to 163 move towards additional invasive interventions, if needed. As long as fetal monitoring is 164 reassuring, tolerating maternal O2 saturations between 92-96% is prudent and might prevent 165 detrimental outcomes associated with invasive interventions that could negatively affect both 166 mother and baby. 167 In the setting of reassuring fetal heart rate monitoring, this could possibly prevent 186 unnecessary invasive interventions including endotracheal intubation with mechanical ventilation 187 and ECMO. This is especially significant when the decision to escalate towards these measures 188 is based on the concern for maintaining fetal oxygenation rather than supporting the mother's 189 respiratory status. In these situations, external fetal monitoring can be used as an additional non- 

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