The impact of isolated single umbilical artery on labor and delivery outcome

Objective: Data regarding the association between isolated single umbilical artery (SUA) and pregnancy outcome are inconsistent and mainly address the risk of pregnancy complications. Thus, we aimed to focus on the association between isolated SUA, and labor and delivery. Methods: We conducted a case-control study of all singleton pregnancies diagnosed with isolated SUA (no known chromosomal/structural anomalies/fetal growth restriction) attempting vaginal delivery. Obstetric and neonatal outcome was compared with that of a control group of pregnancies with a three-vessel cord in a 1:2 ratio matched by parity. Composite adverse outcome included the following: Cesarean section (CS) and/or operative delivery due to non-reassuring fetal heart rate (NRFHR), prolonged neonatal admission, low Apgar score and umbilical artery pH<7.2. Results: Out of 34196 deliveries, 162 (0.5%) were diagnosed with SUA, and 91 (0.27%) were diagnosed with isolated SUA. Isolated SUA was associated with a higher rate of CS due to NRFHR (5.5% vs 1%, p=0.02), small for gestational age (SGA) (14.3% vs 4.9%, p=0.009), lower birth weight, and a higher rate of composite adverse outcome (20.9% vs 8.8%, p=0.005). On multivariable analysis, isolated SUA was independently associated with an increased risk for composite adverse outcome (OR 2.34, 95% CI 1.05-5.21). Conclusion: Isolated SUA is associated with increased risk for CS due to NRFHR and increased rate of SGA.