title: Biophysical interaction between blood pressure and uterine artery Doppler for the occurrence of early-onset preeclampsia: A prospective cohort study.
abstract: OBJECTIVE
  We evaluated the biological interaction between blood pressure (BP) and uterine artery Doppler (UAD) in the second trimester for early-onset preeclampsia (EO-PE) risk.
  
  
  METHODS
  A prospective cohort study.
  
  
  METHODS
  In 2410 pregnant women, mean pulsatility index (mPI) and mean notch depth index (mNDI) were examined by UAD at 16-23weeks' gestation. We defined EO-PE as PE with onset at <34weeks, abnormal UAD as coexistence of mPI⩾90th percentile and mNDI⩾90th percentile, and high BP as systolic BP/diastolic BP⩾120/80mmHg. 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.
  
  
  RESULTS
  EO-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.
  
  
  CONCLUSIONS
  High BP and abnormal UAD may have a strong biological interaction for the occurrence of EO-PE.
authors.affiliation: Department of Obstetrics and Gynecology, Jichi Medical University School of Medicine, Tochigi, Japan.
authors.forename: Kayo
authors.initials: K
authors.lastname: Takahashi
authors.affiliation: Department of Obstetrics and Gynecology, Jichi Medical University School of Medicine, Tochigi, Japan. Electronic address: okuchi@jichi.ac.jp.
authors.forename: Akihide
authors.initials: A
authors.lastname: Ohkuchi
authors.affiliation: Department of Obstetrics and Gynecology, Jichi Medical University School of Medicine, Tochigi, Japan.
authors.forename: Hirotada
authors.initials: H
authors.lastname: Suzuki
authors.affiliation: Department of Obstetrics and Gynecology, Jichi Medical University School of Medicine, Tochigi, Japan.
authors.forename: Rie
authors.initials: R
authors.lastname: Usui
authors.affiliation: Department of Obstetrics and Gynecology, Jichi Medical University School of Medicine, Tochigi, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Kuwata
authors.affiliation: Division of Inflammation Research, Center of Molecular Medicine, Jichi Medical University, Tochigi, Japan.
authors.forename: Koumei
authors.initials: K
authors.lastname: Shirasuna
authors.affiliation: Department of Obstetrics and Gynecology, Jichi Medical University School of Medicine, Tochigi, Japan.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Matsubara
authors.affiliation: Department of Obstetrics and Gynecology, Jichi Medical University School of Medicine, Tochigi, Japan.
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Suzuki
keywords: Biological interaction; Blood pressure level; Prediction; Preeclampsia; Uterine artery Doppler