Modelling lowering of elevated blood pressure in pregnancy to reduce pre-eclampsia

Objective: To determine whether antihypertensive treatment of blood pressure below 140/90mmHg may reduce the incidence of pre-eclampsia. Design: Modelling study of blood pressure lowering from early pregnancy, on the impact of pre-eclampsia, as a secondary analysis of data from prospective non-intervention cohort studies. Setting: Seven secondary care institutions in England. Participants: 54,422 pregnancies who underwent screening at 11-13 weeks’ gestation for pre-eclampsia, with blood pressure values available, and who gave birth to a liveborn or stillborn infant at ≥24 weeks’ gestation. Excluded were pregnancies with aneuploidy, major fetal abnormality, and those ending in miscarriage or termination before 24 weeks’ gestation. Interventions: The Fetal Medicine Foundation competing-risks model was used to calculate the expected pre-eclampsia risk, based on maternal characteristics, mean arterial pressure, uterine artery pulsatility index, and placental growth factor. Expected pre-eclampsia risks were used to calculate expected PE incidence. To model the effect of lowering diastolic blood pressure from over 85, 80, or 75mmHg throughout pregnancy, diastolic blood pressure was fixed at these values, systolic blood pressure modelled, mean arterial pressure and pre-eclampsia risk recalculated, and expected pre-eclampsia incidence re-estimated. Results were expressed as relative risk reduction (RRR). Main outcome measures: Pre-eclampsia incidence (overall, and at preterm or term gestational ages), according to modelled blood pressure lowering. Results: The study population was ethnically diverse (17.3% Black, 7.8% South/East Asian, and 2.6% with >1 self-identified ethnicity). Reducing diastolic blood pressure >85mmHg to 85mmHg, 4.8% of women would receive antihypertensives, with a potential RRR of 21.4% (absolute reduction of 2.9%) in any pre-eclampsia and 28.32% (absolute reduction of 1.4%) in preterm pre-eclampsia. Reducing diastolic blood pressure >80mmHg to 80mmHg, 13.2% would receive antihypertensives, with a potential RRR of 26.0% (absolute reduction of 2.3%) in any pre-eclampsia and 33.8% (absolute reduction of 1.0%) in preterm pre-eclampsia. Reducing diastolic blood pressure >75mmHg to 75mmHg, 29.5% would receive antihypertensives, with a potential RRR of 32.8% (absolute reduction of 2.1%) in any pre-eclampsia and 41.6% (absolute reduction of 0.8%) in preterm pre-eclampsia. Conclusions: Lowering blood pressure from early pregnancy may reduce preterm and term pre- eclampsia. This requires evaluation in a definitive, randomised trial.