Pre-eclampsia: reducing the risk with calcium supplements

Pre-eclampsia (raised blood pressure and proteinuria) complicates 2% to 8% of pregnancies, and increases morbidity and mortality in the mother and child. Pre-eclampsia is more common in older women, women with a high body mass index, and women with multiple pregnancy. Pre-eclampsia risk is also increased in women with underlying medical conditions, particularly conditions associated with microvascular disease.

We conducted a systematic overview, aiming to answer the following clinical questions: Does oral calcium supplementation during pregnancy reduce the risk and/or severity of pre-eclampsia? What are the effects of preventive calcium supplements pre-conception in women at risk of pre-eclampsia? We searched: Medline, Embase, The Cochrane Library, and other important databases up to November 2014 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review).

At this update, searching of electronic databases retrieved 109 studies. After deduplication and removal of conference abstracts, 55 records were screened for inclusion in the overview. Appraisal of titles and abstracts led to the exclusion of 30 studies and the further review of 25 full publications. Of the 25 full articles evaluated, one update of a previously included systematic review was added. We performed a GRADE evaluation for seven PICO combinations.

In this systematic overview, we categorised the efficacy for three interventions based on information about the effectiveness and safety of calcium supplementation used to prevent pre-eclampsia, both during pregnancy and pre-conception, and different doses of calcium supplementation versus each other during pregnancy.