Providing calcium supplements to women who are deficient in the mineral can lower the incidence of several severe complications of pregnancy, according to research published in the American Journal of Obstetrics and Gynecology.

The study conducted by a global team of investigators under the auspices of the World Health Organisation (WHO), aimed to find out whether a calcium supplement could reduce the complications and mortality caused by preeclampsia — the development of high blood pressure and protein in the urine during pregnancy.

A link to calcium deficiency had been suggested by earlier research. Preeclampsia and its more severe complications — such as eclampsia — can threaten the lives of both mother and child. Over 8,300 women with low dietary calcium — that is, less than 600 mg per day, which is about half of that recommended during pregnancy — were selected for the study. The subjects were randomly divided into two groups that had similar gestational ages, demographic characteristics, and normal blood pressures before treatment started. Half were given 1.5g of a calcium supplement per day and half received a placebo. "While supplementation with 1.5 gm calcium/day did not result in a statistically significant decrease in the overall incidence of preeclampsia, calcium significantly decreased the risk of its more serious complications, including maternal and severe neonatal morbidity and mortality," states author Jose Villar, MD.

The incidence of severe gestational hypertension was significantly lower. Preterm and early preterm delivery — that is, at less than 32 weeks — tended to be reduced among women under 20 years of age who were at highest risk for low calcium and complications. Neonatal mortality also was lower in the calcium group, the researchers pointed out.