Antenatal detection of a single umbilical artery: does it matter?

The presence of a single umbilical artery is recognised as a soft marker for congenital anomalies, aneuploidy, earlier delivery and low birthweight. Most of the available data are derived from case series or highly selected populations and are therefore likely to be unrepresentative. In this retrospective case-comparison study, we firstly aimed to determine the incidence of a single umbilical artery in an unselected population and secondly to examine the clinical significance of this soft marker. Over a 40-month period, 107 cases were identified from a cohort of 35 066 births giving an incidence of 3.1 per 1000 total births and late pregnancy losses. The antenatal detection rate was only 30%. Compared to fetuses with normal cord vasculature, fetuses with a single umbilical artery were more likely to be delivered at an earlier gestation and to weigh less, were 1.7 times more likely to be delivered by a Caesarean section and 19% of the cases had a congenital anomaly. The perinatal mortality was 49.0 per 1000 total births, which was 6 times higher than the background hospital rate. The presence of a single umbilical artery is associated with a poorer perinatal outcome compared to that in fetuses with three vessels in the cord. Unfortunately, the antenatal detection rate is poor. Recognising the importance of this soft marker in counselling and management of pregnancies should provide the stimulus to improve detection rates.