Modelling lowering of raised blood pressure in pregnancy to reduce pre-eclampsia: secondary analysis of data from prospective cohort studies

Objective To determine whether antihypertensive treatment of blood pressure levels of <140/90 mm Hg can reduce the incidence of pre-eclampsia.Design Secondary analysis of data from prospective cohort studies.Setting Three prospective screening studies of women who attended routine hospital maternity visits at 11-13 weeks' gestation, 1 February 2010 to 31 December 2016. Participants were from seven secondary care institutions in England.Participants 54 422 pregnancies screened at 11-13 weeks' gestation for pre-eclampsia and with blood pressure values available, that resulted in a liveborn or stillborn infant at ≥24 weeks' gestation.Main outcome measures Incidence of pre-eclampsia (overall, and at preterm or term gestational ages), according to modelled blood pressure lowering.Results The study population was ethnically diverse (17.3% black participants, 7.8% from South or East Asia, and 2.6% self-identified with more than one ethnic group). The Fetal Medicine Foundation competing risks model was used to calculate the expected risk of pre-eclampsia, based on maternal characteristics, mean arterial pressure, uterine artery pulsatility index, and placental growth factor. The expected risk of pre-eclampsia was used to calculate the expected incidence of pre-eclampsia. Reducing diastolic blood pressure from >85 mm Hg to a target of 85 mm Hg would mean that 4.8% of women would be offered antihypertensive drugs, with a potential relative risk reduction of 21.4% (absolute reduction of 2.9%) in any pre-eclampsia and 28.3% (absolute reduction of 1.4%) reduction in preterm pre-eclampsia. By reducing diastolic blood pressure from >80 mm Hg to a target of 80 mm Hg, 13.2% of women would receive antihypertensive drugs, with a potential relative risk reduction of 26.0% (absolute reduction of 2.3%) in any pre-eclampsia and 33.8% (absolute reduction of 1.0%) reduction in preterm pre-eclampsia. By reducing diastolic blood pressure from >75 mm Hg to a target of 75 mm Hg, 29.5% of women would receive antihypertensive drugs, with a potential relative risk reduction 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 finding requires evaluation in a definitive randomised trial.