Evaluation of midtrimester ductus venosus diameter and peak systolic velocity to predict late onset small for gestational age fetuses.

OBJECTIVE: The ductus venosus, a small blood vessel in the fetal venous system, has extraordinary physiologic significance because it connects the umbilical vein to the inferior vena cava in the fetus circulation system and transports highly oxygenated blood from the placenta to the fetus' heart. Hence, assessment of ductus venosus flows is helpful in evaluating fetal hemodynamics. Considering the critical function of the ductus venosus, we hypothesized that the diameter of the midtrimester ductus venosus and its peak velocity index can be related to adequate fetal growth; therefore, the aim of this study was to evaluate the role of the midtrimester umbilical venous blood flow, ductus venosus diameter, and ductus venosus peak systolic velocity to help predict uncomplicated deliveries of late onset small for gestational age (SGA) fetuses.

METHODS: In this prospective study we analyzed the pregnancies and deliveries of 398 pregnant women who met the inclusion criteria and divided them into three groups according to fetal birth weight as follows: birth weight <3 percentile SGA group ( n  = 16), birth weight 3-10 percentile SGA group ( n  = 42), and appropriate for the gestational age (AGA) group ( n  = 340). The midtrimester ductus venosus diameter and peak sistolic velocity, umbilical venous blood flow, and umbilical artery pulsatility index (PI) were recorded. In the absence of congenital anomalies, the diagnosis of fetal growth restriction (FGR) is made according to Delphi consensus criteria. In the absence of abnormal Doppler findings, late FGR was defined as occurring ≥32 weeks.

RESULTS: Maternal age, nulliparity, mean gestational age at ultrasound evaluation, ethnicity, body mass index, and previous cesarean delivery rates were similar among the groups. In addition, mid-trimester fetal biometric measurements and amniotic fluid volume were similar among the groups. The gestational age at delivery, prematurity, fetal birth weight, vaginal delivery rates, and rate of admission to the neonatal intensive care unit were significantly different among the groups. The mean mid-trimester umbilical vein blood flow to abdominal circumference ratio (UVBF/AC) was similar among the groups ( p =.740). In the <3 group, the mean peak systolic velocity of the ductus venosus was significantly lower and the mean diameter of the ductus venosus significantly higher than those in the 3-10 and AGA groups (both p <.001). Although the values are below the 95th percentile mid-trimester umbilical artery PI was significantly higher in the <3 percentile SGA group than in the 3-10 percentile SGA and AGA groups.

CONCLUSION: Our results suggest that the diameter and peak systolic velocity of the mid-trimester ductus venosus are useful noninvasive measurements that provide prediction of late onset SGA fetuses.