The value of Doppler ultrasonography in prolonged pregnancies.

One hundred forty-two gravid women at term were followed prospectively by a non-stress test, estimation of amniotic fluid volume and Doppler velocimetry of the umbilical and uterine arteries. Adverse perinatal outcome was detected in 12 women (8.5%). Abnormal antepartum tests were detected in 26 women (17%). Seven women had an abnormally elevated resistance index (RI) in the umbilical artery; but only two had an abnormal outcome. Seven women had an abnormally elevated RI in the uterine artery, but only two had abnormal outcome. Three out of 11 women with oligohydramnion had abnormal perinatal outcome. Only one out of seven women with an abnormal non-stress test had abnormal perinatal outcome. In six women, more than one antepartum test was abnormal. The various surveillance methods demonstrated a low sensitivity (the highest was obtained by estimating amniotic fluid volume: 25%) and a low positive predictive value (the highest obtained by measuring the resistance index in either the umbilical or the uterine arteries: 28.6%). By considering any abnormal test as a positive test result for a given patient, a substantial improvement in sensitivity (66.7%) and positive predictive value (33.3%) are obtained. Doppler velocimetry adds very little in itself to the follow-up of patients with post-term gestations. However, when combined with additional antepartum tests, it may increase our ability to predict the compromised fetus in this condition.