The researchers studied 8,325 pregnant women without hypertension from seven countries, including the UK, whose daily calcium intake was lower than 600mg.
The women were randomly assigned to receive a 1.5g daily calcium supplement or placebo throughout pregnancy.
Supplementation was found to reduce pre-eclampsia rates, but not significantly.
It reduced the risk of eclampsia by 32 per cent and of severe gestational hypertension by 29 per cent. Neonatal mortality was 30 per cent lower in the calcium group.
Am J of Obstet Gynecol 2006; 194: 639-49