CAP trial Blood pressure

The hypothesis that early pregnancy calcium supplementation modifies the pathogenesis of pre-eclampsia by having a direct effect on blood pressure. This is the data used for a secondary analysis of a parallel arm, double-blind, randomised trial in South Africa, Zimbabwe and Argentina (PACTR201105000267371). Participants with previous pre-eclampsia/eclampsia received 500 mg calcium or placebo daily from enrolment pre-pregnancy until 20 weeks’ gestation. Both groups received unblinded calcium 1.5g daily after 20 weeks. We compared blood pressures between groups at 20 and 32 weeks’ gestation and investigated the effect of compliance on the two main trial outcomes. We compared diastolic and systolic blood pressures between calcium and placebo groups at 20 weeks’ and at 32 weeks’ gestation. We also investigated the effect of compliance from the last visit before pregnancy to 20 weeks’ gestation (25%, 50%, 75%, and 80%) on blood pressure and the main trial results (pre-eclampsia, and ‘pregnancy loss or pre-eclampsia’). The sample size for the current sub-study was opportunistic and based on the main study primary outcome (pre-eclampsia). Analyses were conducted by intention-to-treat (ITT), as well as at varying levels of compliance.