Prenatal diagnosis of single umbilical artery: determination of the absent side, associated anomalies, Doppler findings and perinatal outcome.

OBJECTIVE: To determine the absent side of a single umbilical artery and its association with malformations and abnormal karyotypes.
METHODS: We prospectively studied 102 fetuses from 13 to 39 weeks of gestational age with a prenatally identified single umbilical artery. The absent side, pregnancy data, Doppler findings and the perinatal outcome were reviewed.
RESULTS: (1) The left umbilical artery was absent in 71 (69.6%) and the right in 31 (30.4%) fetuses; (2) Single umbilical artery as an isolated finding occurred in 59 (57.8%) pregnancies and was not associated with aneuploidy. The mean gestational age at delivery in this group was 38.4 weeks and the mean birth weight was 3047 g. Six (10.2%) fetuses were small for gestational age, all of them with normal umbilical and uterine Doppler findings; and (3) Chromosomal abnormalities were diagnosed in 10 of 43 fetuses with single umbilical artery and congenital malformations. In nine of 10 fetuses with aneuploidy the left umbilical artery was not developed. Absence of the left artery occurred in 21 of 33 fetuses with sonographic anomalies and normal karyotype. Pathologic Doppler measurements of the umbilical artery were found in only one case of nonchromosomal abnormality.
CONCLUSION: Our data suggest that in fetuses with single umbilical artery the absence of the left artery is more frequent than the absence of the right artery. The association with additional malformations seems to be equal on each side.