Predicting fetal distress in growth-restricted fetuses: The role of umbilical vein diameter

This study aimed to evaluate the role of intra-abdominal umbilical vein (FIUV) diameter in predicting fetal distress and the need for emergency cesarean section during labor in fetuses with small-for-gestational-age (SGA) or late-onset fetal growth restriction (late-onset FGR).

A prospective study was conducted between March 2021 and January 2022, involving 51 pregnant women with SGA or late-onset FGR delivering at or beyond 37 weeks' gestation. FIUV diameter was measured via transabdominal ultrasonography, and labor outcomes were assessed. Fetuses were monitored continuously, with cesarean delivery performed for category 3 fetal heart rate tracings. Statistical analyses compared FIUV diameter and FIUV/head circumference (HC) ratios between fetuses with and without distress.

Of the 51 participants, 8 (15.7%) required cesarean delivery due to fetal distress. FIUV diameter was significantly smaller in the distress group (5.20 vs. 8.68 mm; p = 0.006), as well as the FIUV/HC ratio (1.60 vs. 2.65; p = 0.004). Receiver operating characteristic analysis showed AUC values of 0.803 for FIUV and 0.814 for FIUV/HC, with sensitivities of 56.8% and specificities of 100% at cutoff values of 6.2 mm and 1.95, respectively. One-minute Apgar scores were lower in the distress group (6.88 vs. 8.23; p = 0.01).

FIUV diameter is a potential predictor of fetal distress in SGA and late-onset FGR fetuses. Larger FIUV diameters may indicate better fetal adaptation, which in turn reduces labor-related complications. These findings suggest a role for FIUV assessment in guiding delivery planning to improve maternal and neonatal outcomes.