Calcium supplementation to prevent pre-eclampsia--a systematic review.
BACKGROUND
Calcium supplementation during pregnancy may prevent high blood pressure and preterm labour.


OBJECTIVE
To assess the effects of calcium supplementation during pregnancy on hypertensive disorders of pregnancy and related maternal and child adverse outcomes.


METHODS
A systematic review of randomised trials that compared supplementation with at least 1 g calcium daily during pregnancy with placebo.


METHODS
The Cochrane Pregnancy and Childbirth Group trials register (October 2001) and the Cochrane Controlled Trials Register (Issue 3, 2001) were searched and study authors were contacted.


METHODS
Eligibility and trial quality were assessed. Data were extracted and analysed.


RESULTS
There was a modest reduction in the risk of pre-eclampsia with calcium supplementation (relative risk (RR) 0.68, 95% confidence interval (CI): 0.57-0.81). The effect was greatest for women at high risk of hypertension (RR 0.21, 95% CI: 0.11-0.39) and those with low baseline calcium intake (RR 0.32, 95% CI: 0.21-0.49). There was no overall effect on the risk of preterm delivery, although there was a reduction in risk among women at high risk of hypertension (RR 0.42, 95% CI: 0.23-0.78). There was no evidence of any effect of calcium supplementation on stillbirth or death before discharge from hospital. There were fewer babies with birthweight < 2,500 g (RR 0.83, 95% CI: 0.71-0.98). In one study, childhood systolic blood pressure > 95th percentile was reduced (RR 0.59, 95% CI: 0.39-0.91).


CONCLUSIONS
Calcium supplementation appears to be beneficial for women at high risk of gestational hypertension and in communities with low dietary calcium intake. These benefits were confined to several rather small trials, and were not found in the largest trial to date, conducted in a low-risk population. Further research is required.
Hofmeyr
G J
GJ
Effective Care Research Unit, East London Hospital Complex, University of the Witwatersrand, Johannesburg/Fort Hare University, East London, E Cape.
Roodt
A
A
Atallah
A N
AN
Duley
L
L
D002118:Calcium / Q000627:therapeutic use*; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000517:prevention & control*; D011225:Pre-Eclampsia / Q000209:etiology / Q000517:prevention & control*; D011247:Pregnancy; D011248:Pregnancy Complications / Q000517:prevention & control*; D011256:Pregnancy Outcome
D002118:Calcium