Doppler flow velocities in single umbilical arteries

Fetal compromise has been associated with an umbilical artery waveform pattern of low or absent diastolic velocity relative to systolic velocity. Fetuses with single umbilical arteries have an increased risk of major malformations, mortality, retarded fetal growth, and prematurity. In this study Doppler flow velocities were obtained in 13 fetuses (four twin fetuses and nine singletons) with a single umbilical artery. Five (38%) fetuses, consisting of four singletons and one twin, had anomalies. Six (46%) fetuses were small for gestational age, including two twin fetuses and three singleton fetuses with anomalies. Three (23%) of the 13 systolic-to-diastolic velocity ratios were abnormally high. Whereas this is a higher rate of abnormal ratios than the reported 2% to 3% in control populations, it is interesting to note that 77% of fetuses with single umbilical arteries had normal systolic-to-diastolic ratios.