| Summary: | Abstract Background Hypoxia delays brain maturation and contributes to neurodevelopmental morbidity in fetuses with congenital heart defects (CHDs). Maternal hyperoxygenation (MH) can, in theory, promote oxygen/nutrient delivery to the fetal brain, owing to an improved heart structure/function and increased fetal oxygen content. We aimed to determine whether MH alters fetal cerebral hemodynamics in fetuses with CHD. Methods Twenty-eight fetuses with borderline small left hearts and 28 age-matched normal fetuses were enrolled and subdivided by gestational age (GA): 23+ 0 ~ 27+ 6 weeks and 28+ 0 ~ 36+ 6 weeks. The middle cerebral artery pulsatility index (MCA-PI), vascular index (VI), flow index (FI) and vascular/flow index (VFI) were measured with baseline room air, after 10 min of MH and after 10 min of recovery for all subjects. Results MCA-PI, VI, FI and VFI did not differ with MH in the normal fetuses. In fetuses with borderline small left hearts, MCA-PI increased and VI, FI and VFI significantly decreased during the 3rd trimester (from 1.44 ± 0.27, 3.19 ± 0.87, 56.91 ± 9.19, and 1.30 ± 0.33 at baseline to 1.62 ± 0.15, 2.37 ± 0.37, 45.73 ± 4.59, and 0.94 ± 0.15 during MH, respectively, P < 0.05), but this response was not apparent during mid-gestation (p > 0.05). These parameters returned to the baseline levels during the recovery phase. The change in cerebral perfusion depended on the baseline MCA-PI and increased the combined cardiac index (CCOi). Conclusions MH alters the cerebral hemodynamics of fetuses with borderline small left hearts during the third trimester. Further investigation is needed to determine whether MH may benefit brain growth and neurodevelopment in this high-risk population.
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