Effects of Maternal Hyperoxygenation on Fetal Hemodynamics Assessed by Ultrasound and Fetal Echocardiography in Congenital Heart Disease: A Systematic Review and Single Arm Meta‐Analysis

OBJECTIVES: To evaluate the effects of maternal hyperoxygenation (MH) on fetal hemodynamic parameters assessed by ultrasound and fetal echocardiography in pregnancies complicated by congenital heart disease (CHD). METHODS: A systematic review and single-arm meta-analysis were conducted according to PRISMA guidelines and registered in PROSPERO (CRD420251274436). PubMed, EMBASE, and Cochrane Central were searched for studies evaluating fetal hemodynamic changes before and during MH in fetuses with prenatally diagnosed CHD. Continuous outcomes were pooled as mean changes using inverse-variance random-effects models. Risk of bias was assessed with ROBINS-I and Joanna Briggs Institute tools, and the certainty of evidence was graded using GRADE. Middle cerebral artery Z-score (MCA-Z) was defined as the standardized deviation of the Doppler pulsatility index from gestational age-adjusted reference values. Pulmonary velocity time integral (VTI) was measured by Doppler at the level of the fetal pulmonary artery to estimate pulmonary flow. RESULTS: Overall, MH was associated with reduced MCA-Z score and increased pulmonary VTI, indicating cerebral circulatory adaptation and augmented pulmonary flow parameters among the nine observational studies included. Substantial heterogeneity was observed, mainly related to study design, confounding, and variability in MH protocols and Doppler methods. CONCLUSIONS: In fetuses with CHD, MH is associated with consistent cerebral Doppler changes and selected pulmonary flow adaptations. These findings support MH primarily as a physiological assessment tool rather than a routine therapeutic intervention. Further standardized studies are needed to clarify its clinical relevance.