NEW YORK (Reuters Health, AsiaOne) - Pregnant women who take calcium supplements reduce their risk of developing preeclampsia, sometimes called toxemia of pregnancy, according to a new study.

Sometimes referred to as pregnancy-induced hypertension, preeclampsia is defined by high blood pressure and excess protein in the urine after 20 weeks of pregnancy.

Calcium supplementation, however, has no effect on the risk of preterm birth or stillbirth.

Dr. G. J. Hofmeyr, of the University of the Witwatersrand/University of Fort Hare, East London, South Africa, and colleagues conducted a systematic review of 12 clinical trials, involving over 15,500 women, that compared at least 1 gram of calcium daily during pregnancy with an inactive "placebo" supplement.

Most of the women were at low risk for pregnancy complications, but they had low levels of calcium in their diet. Compared with placebo, calcium supplementation was associated with less high blood pressure and less preeclampsia, the investigators report in the British Journal of Obstetrics and Gynecology.

No overall effect was seen on the risk of preterm birth or stillbirth or infant death before hospital discharge.

"Calcium supplementation during pregnancy for women with deficient dietary calcium intake offers modest benefit for individual women," Hofmeyr's team concludes.

"However, a public health policy of calcium supplementation during pregnancy is unlikely to have a major impact on the incidence of pre-eclampsia," they continue, because in those communities where dietary calcium is inadequate, high-risk women "often attend antenatal clinics late in pregnancy or not at all and so would not benefit from strategies directed at those attending for antenatal care."

The researchers therefore suggest "that future research be directed towards evaluation of improving calcium intake at a population level, for example by food fortification, rather than at an individual level."

SOURCE: British Journal of Obstetrics and Gynecology, August 2007.