Prediction of preeclampsia by uterine artery Doppler at 20-24 weeks' gestation.

Objectives: To determine maternal characteristics affecting uterine artery pulsatility index (PI) in normal pregnancies at 20-24 weeks' gestation and examine in pregnancies with preeclampsia (PE) the relation between uterine artery PI multiple of the median (MoM) and severity of disease.
Methods: Uterine artery PI was measured at 20-24 weeks in 50,490 singleton pregnancies, including 1,442 (2.9%) that developed PE. Uterine artery PI was expressed as MoM after adjustment for maternal characteristics and corrected for adverse pregnancy outcomes. In PE, the correlation between uterine artery PI MoM with gestational age at delivery and birth weight Z-score was determined.
Results: In the normal group there were significant independent contributions to uterine artery PI from gestational age, racial origin and prior history of PE, and/or small for gestational age (SGA). In the PE group, there was an inverse significant association between uterine artery PI MoM and both gestational age at delivery and birth weight Z-score (p < 0.0001). Uterine artery PI was above the 95th percentile (1.509 MoM) in 72.7, 36.1 and 14.9% of cases of PE requiring delivery at <34, 34-37 and ≥38 weeks, respectively, and the percentages for PE with SGA were 80.2, 55.6 and 37.4%.
Conclusions: In a normal pregnancy, uterine artery PI is affected by maternal characteristics, and in PE, uterine artery PI MoM is related to the severity of the disease.