Abstract

Background: The fetal liver is perfused by the umbilical vein (UV) and the main portal vein (MPV), both of which are crucial for nutrient delivery. The configuration of the umbilicoportal anastomosis may influence MPV blood flow and potentially affect fetal liver perfusion in fetuses with fetal growth restriction (FGR).

Aims: To evaluate absolute and normalized UV and MPV blood flows in fetuses with normal growth and FGR, and to investigate the effect of umbilicoportal anastomosis type on MPV flow.

Study Design: This prospective case–control study included 108 appropriate-for-gestational-age (AGA) fetuses and 43 FGR fetuses between 18 and 37 weeks of gestation, evaluated over nine months.

Methods: Ultrasound was used to measure UV and MPV diameters, while Doppler ultrasound assessed time-averaged maximum velocities. Flow volumes were calculated as time-averaged maximum velocity volume and normalized to estimated fetal weight (TAMXVVN) and abdominal circumference. Anastomoses were categorized as T-, X-, or H-shaped. Z-scores were derived from AGA nomograms.

Results: Compared with AGA fetuses, FGR fetuses exhibited significantly smaller UV diameters, lower absolute UV flow, UV-TAMXVVN, and UV-TAMXVV/AC (p < 0.05), but higher MPV-TAMXVVN (p < 0.05), suggesting compensatory redistribution. Both UV and MPV flows showed strong correlations with gestational age (r > 0.7, p < 0.001). UV-TAMXVVN Z-scores decreased with gestation, whereas MPV-TAMXVVN Z-scores increased until 32 weeks before plateauing. Blood flow parameters did not differ significantly across anastomosis types in either group.

Conclusion: FGR fetuses demonstrate reduced UV perfusion with compensatory increases in MPV flow. The type of umbilicoportal anastomosis does not significantly affect MPV blood flow.