By: Thomas Pickering, MD, DPhil, FRCP, Director of Integrative and Behavioral Cardiology Program
of the Cardiovascular Institute at Mount Sinai School of Medicine, New York.

About five percent of pregnant women develop high blood pressure (preeclampsia, or toxemia) during the second half of pregnancy. This is a leading cause of maternal death, and can also result in still-births and small babies. The hypertension usually disappears after delivery as mysteriously as it came, and its cause remains unknown. Several small studies have suggested that giving extra calcium to women during pregnancy may help to prevent it, but the results have been inconclusive. A large American study, the Calcium for Preeclampsia Prevention, which was conducted in five US medical centers, has now reported its results.

Four thousand, five hundred and eighty-nine pregnant women were randomly allocated to receive either calcium (2,000 milligrams a day as calcium carbonate) or inert placebo when they were 13 to 21 weeks pregnant. Calcium had no effect on either the rate of pre-eclampsia, which was about 7% in both groups or on the outcome of the pregnancy.

Doctor's comments

This is by far the largest and most carefully conducted study of calcium supplementation to prevent preeclampsia, and it is disappointing that it showed no hint of any benefit, even in women who had a low-calcium intake to begin with. Preeclampsia is different from ordinary or essential hypertension in that it usually goes away after delivery, and often does not recur in subsequent pregnancies.

Where it was published