The role of calcium in pre-eclampsia and gestational hypertension

Pre-eclampsia is one the major causes of maternal mortality and pre-mature delivery (<37 weeks gestation) which can cause infant mortality. Blood pressure changes in pregnancy, falling early on then rising to pre-pregnancy levels at term. This fluctuation can make the diagnosis of gestational hypertension more difficult. When hypertension is accompanied by proteinuria, the diagnosis is more serious and is termed “pre-eclampsia”.  A diet low in calcium may trigger the release of parathyroid hormone or renin that increases intracellular calcium in smooth muscle lining blood vessels and thereby cause vasoconstriction. This vasoconstriction increases the total peripheral resistance and thus raises the blood pressure. Similarly, calcium supplementation can lower peripheral resistance and blood pressure by not elevating PTH and renin levels. Additionally, it can reduce contractility of the uterine smooth muscles and thus prevent premature delivery.

This Cochrane review based on 13 randomized controlled trials involving 15,370 women found that calcium supplementation of >1g/d reduced pre-eclampsia (RR 0.45) and preterm birth compared to placebo treatment. However, there was no effect of calcium on the risk of stillbirth or death before discharge from hospital. The calcium supplementation began between 13-32 weeks of gestation in the various RCT.

Calcium is present in PM Procare (Pregnancy & Breastfeeding formula); AB Extra Bone-Care+ (Comprehensive Calcium Supplement), PM NextG Cal (Strengthen bones, tissues and teeth with MCHA), and PM Kiddiecal (Chewable Calcium Supplement)

Reference
Hofmeyr, G.J., et al., Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems. Cochrane Database Syst Rev, 2010(8): p. CD001059.