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.