Antenatal assessment of discordant umbilical arteries in singleton pregnancies.

AIM To assess the relationship between discordant umbilical arterial size and resultant blood flow parameters and determine the impact of discordance on fetal outcome. METHODS This is a descriptive, cross-sectional study of 200 patients with a singleton gestation, who underwent a fetal anatomy survey between 18 to 23 weeks of gestation, with documented umbilical cord morphological patterns and blood flow characteristics. Umbilical vessel diameters and Doppler parameters (umbilical vein blood flow volume, mean resistance index, and peak-systolic velocity) were analyzed for discordance. Discordances encountered were examined for their possible association with perinatal outcome. RESULTS We had adequate ultrasound umbilical cord images, Doppler flow parameters, and all necessary demographic data for 154 patients. Umbilical artery discordance averaged 13.1% and was significantly correlated with both the expected and the true percent of difference in resistance index values (RI, P<0.001). In 12 patients (7.8%), a significant discordance of more than 29.5%, or 95th percentile, was observed between the two umbilical artery diameters. However, in these cases no associated adverse perinatal outcome or significant placental pathology was noted. There was no significant difference between patients discordant or concordant umbilical artery in terms of maternal, labor, and neonatal data. CONCLUSION The magnitude of umbilical arteries' luminal discordance directly influences the corresponding blood flow parameters. In our sample of patients, the presence of discordant-in-size umbilical arteries was not associated with umbilical cord or placental abnormalities.