Screening for placental insufficiency by uterine artery doppler

Doppler ultrasound provides a non-invasive method for the study of the uteroplacental circulation. In normal pregnancy, impedance to flow in the uterine arteries decreases with gestation, which may be the consequence of trophoblastic invasion of the spiral arteries and their conversion into low-resistance vessels. Preeclampsia and intrauterine growth restriction are associated with failure of trophoblastic invasion of spiral arteries, and Doppler studies in these conditions have shown that impedance to flow in the uterine arteries is increased. A series of screening studies involving assessment of impedance to flow in the uterine arteries have examined the potential value of Doppler in identifying pregnancies at risk of the complications of impaired placentation. This review examines the findings of Doppler studies in unselected populations that provided sufficient data to allow calculation of the performance of the test. The literature search identified 15 such studies, but they provided discrepant results, which may be the consequence of differences in Doppler technique for sampling, the definition of abnormal flow velocity waveform, differences in the populations examined, the gestational age at which women were studied, and different criteria for the diagnosis of pre-eclampsia and intrauterine growth restriction. Nevertheless, the studies provided evidence that increased impedance to flow in the uterine arteries is associated with increased risk for subsequent development of pre-eclampsia, intrauterine growth restriction and perinatal death. In addition, women with normal impedance to flow in the uterine arteries constitute a group that have a low risk of developing obstetric complications related to uteroplacental insufficiency. It is possible that increased impedance identifies about 50% of pregnancies that subsequently develop preeclampsia and about 30% of those that develop intrauterine growth restriction. Abnormal Doppler is better in predicting severe rather than mild disease. The sensitivity for severe disease requiring early delivery is about 80% for pre-eclampsia and 60% for intrauterine growth restriction.