Maternal Hyperoxygenation for Prenatal Risk Stratification of Pulmonary Venous Obstruction in Total Anomalous Pulmonary Venous Return.

Pulmonary venous obstruction (PVO) is a major determinant of early morbidity and mortality in neonates with total anomalous pulmonary venous return (TAPVR). Accurate prenatal identification of obstructed TAPVR remains challenging due to low pulmonary blood flow in fetal circulation. Maternal hyperoxygenation (MHO) increases fetal pulmonary blood flow and may unmask clinically significant obstruction. We retrospectively reviewed three fetuses with prenatally diagnosed TAPVR who underwent late‑gestation fetal echocardiography with MHO testing. Doppler indices of pulmonary vasoreactivity and vertical vein (VV) flow were assessed at baseline and during MHO and correlated with postnatal clinical outcomes. All fetuses demonstrated preserved pulmonary vasoreactivity during MHO. One fetus had no Doppler evidence of PVO at rest or during MHO and had a stable postnatal course without emergent intervention. One fetus demonstrated elevated VV velocities at baseline that worsened during MHO and required emergent surgical repair shortly after birth. In the third fetus, VV Doppler findings were normal at baseline but became abnormal during MHO, accurately predicting postnatal clinical deterioration and the need for early catheter‑based intervention. These findings suggest that MHO testing can unmask occult pulmonary venous obstruction in fetal TAPVR and may improve prenatal risk stratification and perinatal planning.