Twin pregnancies discordant for single umbilical artery

OBJECTIVE: To evaluate the perinatal outcomes in twin pregnancies discordant for single umbilical artery (SUA). STUDY DESIGN: This was a retrospective cohort study. Our database was searched for all cases of twin gestation and SUA from 1997-2009. We reviewed all the maternal and neonatal records and placental pathology reports. The outcomes of the SUA fetuses were compared to that of their cotwins with a 3-vessel cord (3VC). Paired t test and χ2 tests were used for statistical analyses. RESULTS: We identified 29 cases of twin pregnancies discordant for SUA out of 60,989 ultrasound patients. There were no differences in the prevalence of coexisting anomalies (34% vs. 21%, p=0.38) between the SUA fetus and the 3VC fetus. The SUA fetus was found to have significantly lower mean birth weight (1,784±765 g vs. 2,053±668 g, p=0.001), 1-minute Apgar score (6.83 ± 1.89 vs. 7.62 ± 1.18, p = 0.037), and umbilical artery cord pH (7.27±0.06 vs. 7.31±0.07, p=0.001). The SUA fetus was smaller 79% of the time (p<0.0001). The SUA fetus achieved a significantly lower percentile (12.77%±21.8 vs. 32.00%±27.56, p=0.002) when calculating the customized growth potential. CONCLUSION: The fetus affected by an SUA in a twin gestation has impaired fetal growth and neonatal outcomes when compared to its 3VC counterpart.