Objectives: The present study aimed: 1) to simultaneously investigate the relationship between blood flow volumes of the two fetal liver afferent venous systems of normally appropriate for gestational age newborns. 2) to establish the normal reference range centiles values that will serve as a basis for future investigations.
Methods: A cross-sectional, prospective study of singleton low obstetric risk pregnancies. Doppler examination included the measurement of the umbilical and the main portal vein vessels' diameters and time-averaged maximum velocity. The absolute and per kilogram of estimated fetal weight flow volumes and the ratio between the placental and portal blood volume flow were calculated from these data.
Results: Three hundred and sixty-three pregnant women were included in the study. The umbilical and portal flow volumes' capacity to provide blood flow per kilogram of fetal weight, in the period of maximum fetal growth, was diverse. The placental flow decreased continuously from a mean of 121.2 mL/min/kg at the 20th week of gestation to 64.1 mL/min/kg at the 38th week of gestation. Meanwhile, the portal flow volume per kilogram of fetal weight increased from 9.6 mL/min/kg at 32 weeks of gestation to 10.3 at the 38th week of gestation. This resulted in a decrease in the umbilical to portal flow volume ratio from 13.3 to 9.6 during this period.
Conclusion: Our results indicate that in the period of maximum fetal growth, the placental/portal ratio diminishes emphasizing the portal flow's predominance with low oxygen and nutrient supply to the liver.
Keywords: Doppler; fetal liver; pregnancy; venous system.
© 2023 American Institute of Ultrasound in Medicine.