Impact of varying range of maternal oxygenation targets on fetal oxygenation and fetoplacental circulation in an ovine model of pregnancy.

backgroundOptimal oxygen levels in pregnant mothers undergoing mechanical ventilation are not known. This study examined the effects of four maternal oxygenation ranges on fetal hemodynamics and oxygenation in late-preterm lambs.

methodsThirty-seven ewes were intubated, sedated, and surgically catheterized, while exposed to varying FiO

resultsFetal carotid oxygen content was comparable between hyperoxia and normal oxygenation with stable cerebral oxygen delivery (DO₂: 2.0 ± 1.2 vs. 2.1 ± 1.7 mL/kg/min). In contrast, PaO₂ 55-80 mmHg and <55 mmHg were associated with significantly reduced fetal oxygen content (5.2 ± 3.7 and 4.0 ± 3.1 mL/dL, respectively) versus >150 mmHg, though only <55 mmHg differed significantly from 81-150 mmHg. Cerebral DO₂ trended lower in hypoxemic groups (1.6 ± 1.6 and 1.1 ± 1.1 mL/kg/min) but did not reach significance.

conclusionsMaternal hyperoxia exposure is buffered by the fetoplacental circulation minimizing fetal cerebral risk. When maternal PaO₂ < 80 mmHg, particularly < 55 mmHg, fetal carotid oxygen content declines, potentially compromising cerebral oxygen delivery. IMPACT: Pregnant women are highly susceptible to severe respiratory illness and ARDS, yet guidance on optimal maternal oxygen targets is limited. We investigated how varying maternal PaO₂ levels affect fetoplacental circulation and in-utero oxygenation. Using a large mammalian model of acute maternal hypoxia, we assessed whether maternal ARDSnet oxygenation targets (PaO₂ 55-80 mmHg, SpO₂ 88-95%) can be safely applied in pregnancy. Fetal carotid oxygen content decreased at maternal ARDSnet targets and when below PaO₂ 55 mmHg, with a non-significant trend toward reduced fetal cerebral oxygen delivery. Application of a maternal ARDSnet strategy may lead to suboptimal fetal oxygenation.