Doppler velocimetry discordance between paired umbilical artery vessels and clinical implications in fetal growth restriction

Abstract

Background: Studies revealing a discrepancy in umbilical artery Dopplers between the two umbilical arteries in normally-grown fetuses necessitates further evaluation of the paired umbilical arteries in the setting of fetal growth restriction as this is a critical component in the surveillance of this population.

Objective: Umbilical artery Doppler sampling in fetal growth restriction is typically assessed in 1 umbilical artery in a free loop of cord. Although discrepancies of >20% between the 2 umbilical arteries occur in 1 of 3 normal pregnancies, this has not been assessed in fetal growth restriction. Our objectives were to determine the frequency of discordant Doppler pulsatility indices between paired umbilical arteries in a fetal growth restriction cohort and to determine if sampling of 1 or both arteries alters surveillance or timing of delivery.

Study design: A cohort of 425 growth-restricted fetuses between 25 and 39 weeks of gestation had umbilical artery Doppler pulsatility indices determined from both umbilical arteries in a midsegment of the cord to determine: (1) the discrepancy percentage between paired umbilical artery pulsatility indices and (2) the frequency of both arteries being normal, abnormal, or discordant (pulsatility index < and >95th percentile). To determine what sampling method increased the detection of an abnormal Doppler index, 3 sampling methods were compared: (1) average pulsatility index from both umbilical arteries, (2) pulsatility index from 1 umbilical artery chosen randomly, and (3) highest pulsatility index of the 2 umbilical arteries.

Results: The mean percentage difference between umbilical artery pulsatility indices was 11.7%, and in 15.8% of cases, it exceeded 20%. Both umbilical artery pulsatility indices were normal in 71.1% (302/425), abnormal in 12.2% (52/425), and discordant in 16.7% (71/425) of cases (P<.0001). Of the 3 sampling methods, the pulsatility index was abnormal in: (1) 19.2% (82/425) of cases when averaged from both umbilical arteries, (2) 22.1% (94/425) of cases when choosing 1 umbilical artery at random, and (3) 28.9% (123/425) of cases when the highest umbilical artery pulsatility index was used (P=.003).

Conclusion: In this large fetal growth restriction cohort, the overall discrepancy between the 2 umbilical artery pulsatility indices was 11.7%. Among fetuses with at least 1 abnormal umbilical artery pulsatility index, 71 of 123 (57.7%) had 1 normal pulsatility index and 1 abnormal. Thus, the number of arteries sampled and the sampling method used may alter clinical decision-making, including frequency of surveillance and timing of delivery.

Keywords: Doppler velocimetry; fetal growth restriction; fetal surveillance; intrauterine growth restriction; umbilical artery.