Competing risk model in screening for preeclampsia by mean arterial pressure and uterine artery pulsatility index at 30-33 weeks' gestation.

OBJECTIVE: To assess risk for preeclampsia (PE) based on maternal characteristics, mean arterial pressure (MAP) and uterine artery pulsatility index (Ut-PI) at 30-33 weeks' gestation.

METHODS: Screening study in singleton pregnancies including 2,140 that subsequently developed PE and 83,615 that were unaffected by PE, gestational hypertension or delivery of small-for-gestational-age neonates (normal group). We developed a survival time model for the time of delivery for PE by combination of maternal characteristics and history with MAP and Ut-PI multiple of the median (MoM) values (biophysical test). Data on third-trimester MAP and Ut-PI were available in 350 cases of PE and 13,878 of the normal group. The detection rate of PE requiring delivery within 4, 6 and 8 weeks of the visit was estimated.

RESULTS: In pregnancies with PE the log10 MoM values of MAP and Ut-PI were inversely related to gestational age at delivery. Biophysical testing detected 90, 65 and 53% of PE with delivery within 4, 6 and 8 weeks of the visit, at a fixed false-positive rate of 5%.

INTERPRETATION: Testing by maternal characteristics, Ut-PI and MAP at 30-33 weeks could identify 90% of pregnancies developing PE and requiring delivery within the subsequent 4 weeks.