Single umbilical artery risk factors and pregnancy outcomes.

OBJECTIVE To identify risk factors for fetuses and neonates with single umbilical artery and isolated single umbilical artery (single umbilical artery in the absence of chromosomal abnormalities and structural abnormalities) and to assess whether there is an increased risk for complications during pregnancy, labor, and delivery, and for perinatal morbidity and mortality. METHODS A population-based retrospective cohort analysis of deliveries in Nova Scotia, Canada, between 1980 and 2002 was conducted using the Nova Scotia Atlee Perinatal Database. Risk factors and outcomes for single umbilical artery and isolated single umbilical artery pregnancies were compared with three-vessel-cord pregnancies. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for each outcome using multiple logistic regression to adjust for confounding factors. Separate models were run for single umbilical artery and isolated single umbilical artery. RESULTS There were 203,240 fetuses and neonates available for analysis, with 885 (0.44%) having single umbilical artery and 725 (0.37%) having isolated single umbilical artery. Single umbilical artery fetuses and neonates had a 6.77 times greater risk of congenital anomalies and 15.35 times greater risk of chromosomal abnormalities. The most common congenital anomalies in chromosomally normal fetuses and neonates were genitourinary (6.48%), followed by cardiovascular (6.25%) and musculoskeletal (5.44%). For isolated single umbilical artery, placental abnormalities (OR 3.63, 95% CI 3.01-4.39), hydramnios (OR 2.80, 95% CI 1.42-5.49), and amniocentesis (OR 2.52, 95% CI 1.82-3.51) occurred more frequently than with three vessel cords. Neonates with single umbilical artery and isolated single umbilical artery had increased rates of prematurity, growth restriction, and adverse neonatal outcomes. CONCLUSION Fetuses and neonates with single umbilical artery and isolated single umbilical artery are at increased risk for adverse outcomes. Identification of single umbilical artery is important for prenatal diagnosis of congenital anomalies and aneuploidy. Increased surveillance with isolated single umbilical artery may improve pregnancy outcomes. LEVEL OF EVIDENCE II.