Infants with single umbilical artery studied in a national registry. General epidemiological characteristics.

In this paper, registry data on infants born in Sweden between 1983 and 1986 are reviewed to describe the epidemiological characteristics of infants with single umbilical artery (SUA). During this period 372,066 births were registered with information on the number of umbilical vessels. Our data set contains 1782 SUA infants. The incidence at birth was: in multiple births 0.8%, in infants with chromosome anomalies 6.1% and in singletons without a known chromosome anomaly 0.46%. Incidence was higher in girls than in boys. There were no consistent seasonal variations in the date of presumed conception. Low birthweight (less than 2500 g) and preterm birth (less than 37 weeks) were seen more frequently in SUA singleton infants than in infants with three vessels. At any given gestation, SUA infants had a lower mean birthweight than infants with three vessels. The risk of having a SUA infant was increased in women over 40 years, and slightly increased at or above parity of three.