Prediction of pre-eclampsia by uterine artery Doppler imaging: relationship to gestational age at delivery and small-for-gestational age.

OBJECTIVES To determine the relationship between pre-eclampsia, small-for-gestational age (SGA) and gestational age at delivery, and the effect of this relationship on the prediction of pre-eclampsia by uterine artery Doppler imaging. METHODS This was a multicenter prospective Doppler study of the uterine artery at 22-24 weeks of gestation in unselected women with singleton pregnancies. RESULTS In the 30,639 pregnancies examined, the median uterine artery pulsatility index (PI) was 1.0 and the 95(th) centile was 1.58. In 614 (2%) cases the woman developed pre-eclampsia and in this group there was an inverse significant association between the gestational age at delivery and prevalence of SGA (r = - 0.99, P < 0.0001), and between the gestational at delivery and mean uterine artery PI (r = - 0.51, P < 0.0001) and prevalence of mean uterine artery PI above the 95(th) centile (r = - 0.99, P < 0.0001). The mean uterine artery PI was above the 95(th) centile in 77.2% of women who developed pre-eclampsia requiring delivery before 34 weeks, in 35.9% of those delivering at 34-37 weeks and in 21.9% of those delivering after 37 weeks. The respective percentages were 82.3%, 46.9% and 28.8% for those with pre-eclampsia and SGA, and 43.8%, 21.2% and 8.4% for those with SGA but without pre-eclampsia. CONCLUSIONS Pre-eclampsia requiring early delivery is more likely to be associated with SGA than less severe pre-eclampsia in women who deliver at term. Doppler ultrasound assessment of the uterine arteries is more effective in identifying pre-eclampsia requiring preterm than term delivery.