Calcium supplements could reduce severe pregnancy complications
during pregnancy by 25 per cent, reports a multi-centred WHO study.
Pre-eclampsia occurs during pregnancy when a mother's blood pressure rises to the hypertensive range, and excretion of protein in the urine becomes too high. It is not known why some expectant mothers develop pre-eclampsia.
Eclampsia is a more serious complication of pre-eclampsia and is characterised by convulsions. The condition can be fatal to both mother and baby, with one in 50 mothers and one in 14 babies dying.
The WHO study, published in the March issue of the American Journal of Obstetrics and Gynecology (Vol. 194, pp. 639-649), randomly assigned over 8000 pregnant women with low-calcium intake (less than 600 mg per day) to receive either a daily supplement of 1.5 grams of calcium or an identical-looking placebo.
Women were recruited before week 20 of their pregnancy and took the supplements of placebo until delivery. The tablets were chewable and the calcium was in the form of calcium carbonate.
The baseline characteristics of the women were balanced between the intervention and control groups, and compliance with the programme was similar between the groups: 85 per cent and 86 per cent for calcium and placebo, respectively.
"The incidence of pre-eclampsia was 4.1 per cent in the calcium group and 4.5 per cent in the placebo group with out reaching statistical significant levels," reported lead author José Villar from Department of Reproductive Health and Research, WHO.
"Supplementation with 1.5 grams of calcium per day, however, did reduce the most serious complications of pre-eclampsia significantly, by approximately 25 per cent," said Villar.
Although no study on the mechanism of the benefits of calcium was undertaken for this study, the researchers said that there were new suggestions that "calcium supplementation, perhaps with calciotropic hormones, could blunt the degree of vasoconstriction, thereby reducing disease severity."
Sub-group analysis also revealed that calcium supplementation reduced the occurrence of premature births amongst women younger than 20, a group of women that is at high risk of complications.
Another important results was that general survival rates of the babies increased by 30 per cent in the supplement group.
The study centres were based in six different countries, including Argentina, Egypt, South Africa and India. The tablets, blood pressure equipment, and compliance levels were standard for each centre, all of which are huge strengths for the study.
The main limitation cited by the authors was that the study design was statistically limited to detecting differences of pre-eclampsia greater than 10 per cent.
Villar and colleagues said that the results of this study support the implementation of calcium supplements for calcium deficient women.
Calcium supplements are reported to be the biggest seller in the US supplements industry, with annual sales of about $993 (€836) million in 2004, according to the Nutrition Business Journal.