SINGLE UMBILICAL ARTERY - ANALYSIS OF DOPPLER FLOW INDEXES AND ARTERIAL DIAMETERS IN NORMAL AND SMALL-FOR-GESTATIONAL-AGE FETUSES

In this study we examined the value of Doppler pow measurements of the umbilical artery in distinguishing normal fetuses from those with sin gle umbilical artery, and studied the Doppler flow differences and the compensatory arterial dilatation in appropriate (AGA) and small-for-g estational-age (SGA) fetuses with single umbilical artery. The Doppler pow indices (pulsatility index, SID ratio) and the arterial diameters were prospectively and serially measured in 26 and 15 fetuses with si ngle umbilical artery and without congenital malformations, respective ly. Longitudinal changes in Doppler flow indices in normal and SGA fet uses with single umbilical artery are comparable, and ave within norma l reference ranges for three-vessel cords; there is a fairly constant widening of the single umbilical artery throughout gestation and a mea n increase in size of about I mm over that found in normal cords from 20 weeks onward. In fetuses with single umbilical artery at midgestati on, an umbilical artery diameter of more than 4 mm occurred in only 5/ 15 cases and is therefore not a reliable criterion for single umbilica l artery screening prior to 26 weeks of gestation.Doppler flow measure ments in normal and SGA fetuses with single umbilical artery are not s ignificantly different from normal fetuses. Compensatory arterial dila tation may prevent fetuses with single umbilical artery from becoming growth retarded.