Biophysical interaction between blood pressure and uterine artery Doppler for the occurrence of early-onset preeclampsia: A prospective cohort study

ObjectivesWe evaluated the biological interaction between blood pressure (BP) and uterine artery Doppler (UAD) in the second trimester for early-onset preeclampsia (EO-PE) risk.Study designA prospective cohort study.Main outcome measuresIn 2410 pregnant women, mean pulsatility index (mPI) and mean notch depth index (mNDI) were examined by UAD at 16-23 weeks' gestation. We defined EO-PE as PE with onset at <34 weeks, abnormal UAD as coexistence of mPI ⩾ 90th percentile and mNDI ⩾ 90th percentile, and high BP as systolic BP/diastolic BP ⩾ 120/80 mmHg. Abnormal UAD and high BP were combined as a series of dummy variables, and were entered into a logistic regression model. The relative excess risk due to biological interaction (RERI) was calculated using the following equation: RERI = odds ratio (OR) in women with both high BP and abnormal UAD - OR in women with high BP alone - OR in women with abnormal UAD alone +1. RERI ⩾ 10 was considered as strong.ResultsEO-PE and late-onset PE (LO-PE) occurred in 1.1% and 1.2%, respectively. Adjusted odds ratio (95% CI) in women with abnormal UAD alone, high BP alone, and both high BP and abnormal UAD for predicting EO-PE was 4.3 (0.37-49), 12 (2.6-55) and 85 (17-422), respectively; and that for predicting LO-PE was 6.3 (1.5-27), 6.1 (2.1-17) and 15 (3.6-61), respectively. The RERI for EO-PE and LO-PE was 70 and 3.3, respectively.ConclusionHigh BP and abnormal UAD may have a strong biological interaction for the occurrence of EO-PE.