Maternal hyperoxygenation for the human fetus: should studies be curtailed?

Area of Science:

• Fetal Cardiology
• Neonatal Neurology
• Maternal-Fetal Medicine

Background:

• Congenital hypoplasia of left heart structures (HLHS) is a severe condition affecting fetal development.
• Cerebral development interference is a common complication in fetuses with HLHS.
• Chronic maternal hyperoxygenation (MHO) has been proposed as a therapeutic strategy to improve left heart development and mitigate cerebral damage.

Purpose of the Study:

• To investigate the effects of MHO on fetal cerebral blood flow and metabolism in both normal and HLHS fetuses.
• To evaluate the efficacy of MHO in improving left ventricular size and function in fetuses with HLHS.
• To assess the potential risks of MHO on fetal brain development.

Main Methods:

• Studies involving maternal hyperoxygenation in pregnant ewes and human fetuses.
• Assessment of fetal cardiovascular parameters, including pulmonary blood flow and foramen ovale flow.
• Monitoring of fetal cerebral blood flow, oxygen delivery, and glucose metabolism.

Main Results:

• Maternal hyperoxygenation increased fetal pulmonary blood flow, reducing foramen ovale flow and limiting left ventricular output.
• The effect of MHO on left heart structure size was inconsistent, with some studies reporting modest improvement and others no significant change.
• In sheep fetuses, increased oxygenation led to reduced cerebral blood flow, with decreased cerebral glucose delivery and consumption, despite unchanged oxygen delivery or consumption.
• One study in HLHS fetuses showed MHO was associated with decreased head size.

Conclusions:

• The effectiveness of MHO in improving left ventricular development in fetuses with HLHS is controversial and not consistently demonstrated.
• MHO is associated with reduced fetal cerebral blood flow and may interfere with normal fetal brain development.
• Given the potential adverse effects on cerebral development, further research involving chronic MHO in pregnancy is not recommended, and existing studies should be curtailed.