Evidence for Assessing Effectiveness of Calcium Supplementation in Reducing Risk of Hypertensive Disorders during Pregnancy

High blood pressure, either with or without proteinuria, is one of the most commonly seen medical problems during pregnancy and complicates c. 5–10% of all pregnancies. It is associated with substantial maternal and neonatal mortality worldwide accounting for up to 40,000 maternal deaths annually. For this reason, interventions to reduce the risk of hypertensive disorders of pregnancy have received significant attention. A relationship between high calcium intake and low incidence of preeclampsia has been noted in Ethiopian women and Mayan Indians women of Guatemala. This hypothesis was tested in several studies which suggested a promising beneficial effect for calcium supplementation—although the impact varies according to the baseline calcium intake of the population and preexisting risk factors. It is possible that calcium supplementation reduces parathyroid release and intracellular calcium and thus reduces vasoconstriction. This review examined the effectiveness of calcium supplementation on reducing high blood pressure risk during pregnancy and so promoting maternal and infant health. Searches were made in the Cochrane Data Base of Systematic Reviews, PubMed and CINAHL and meta-analyses, systematic reviews, randomised controlled trials in English since 2005 were reviewed. Six studies were appraised; two of them were meta-analysis studies with level I evidence, two were systematic review studies with level I evidence and two were randomised control trials (RCTs) with level II evidence. Five out of the six studies attested that calcium supplementation is significantly effective in reducing risk of gestational hypertension as well as risk of pre-eclampsia in pregnant women. The effectiveness of calcium supplementation was greater in high-risk pregnant women and in women with a low baseline calcium intake. These findings are significant enough to guide clinical practice. This author therefore recommends 1–2 mg of calcium tablets daily for high-risk pregnant women and for women with a calcium intake of less than 1,000 mg/day. Patient should be advised to take it 3 hours after taking iron tablets and to avoid taking calcium tablets with food rich in iron or caffeine.