Cerebral Hemodynamic Response to Short-Term Maternal Hyperoxygenation in Foetuses with Borderline Small Left Hearts

Objectives: Hypoxia delays brain maturation and contributes to neurodevelopment morbidity in foetuses with congenital heart defects (CHD). Maternal hyperoxygenation (MH) can, in theory, promote oxygen/nutrient delivery to the foetal brain, owing to an improved heat structure/function and increased foetal oxygen content. We aimed to determine whether MH alters foetal cerebral hemodynamic in foetuses with CHD.   Method: Twenty-eight foetuses with borderline small left hearts and 28 age-matched normal foetuses 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 minutes of MH and after 10 minutes of recovery for all subjects. Results: MCA-PI, VI, FI and VFI did not differ with MH in the normal foetuses. A different pattern for the cerebral vascular response to MH was evident in foetuses with borderline small left hearts. MCA-PI increased and VI, FI and VFI decreased significantly during the 3rd trimester, but this response was not apparent during mid-gestation. 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).   Conclusion: MH alters the cerebral hemodynamic of some foetuses with borderline small left hearts during the third trimester. The current data suggest there may be potential negative effect of reducing cerebral blood flow and increasing cerebral vascular resistance.   Funding Statement: This study was supported by the Natural Sciences Foundation of China (no. 81271593, 81501497). Declaration of Interests: The authors state: "None declared" Ethics Approval Statement: This study was approved by the institutional review board at the Second Xiangya Hospital of Central South University, and written informed consent was obtained from all families.