[Doppler flow velocity wave forms of the maternal uterine artery and fetal umbilical artery in normal pregnancy and pregnancy induced hypertension]

Abstract

A simple non-invasive continuous-wave Doppler ultrasound system was used to record the flow velocity wave forms of the maternal uterine artery and the fetal umbilical artery in 113 normal pregnancies and 39 cases of PIH or essential hypertension complicating pregnancy. The systolic/diastolic (S/D) ratio of flow velocities was measured as an index of peripheral resistance. In normal pregnancy the umbilical artery velocity wave S/D ratio declined from 3.9 to 2.1 during the 20th to 40th week while the uterine artery S/D ratio remained constant between 1.8 to 1.9. After the 30th week, either an umbilical artery S/D ratio greater than or equal to 3, or uterine artery S/D ratio greater than 2.6 was defined as abnormal. In 32 PIH cases there were 9 with abnormal umbilical artery S/D ratio and 4 with abnormal uterine artery S/D ratio and the umbilical arterial change seemed to precede the uterine arterial. The rate of abnormal velocity wave forms in PIH was significantly higher than that in normal pregnancy. If both uterine and umbilical artery wave forms were abnormal the fetal outcome was usually poor. The results showed that the method is good for predicting the fetal outcome and once again supported the hypothesis that spasm of arterioles and venules in the placenta leading to high peripheral resistance especially in the fetal side may play an important role in the pathogenesis of PIH.