Calcium supplementation (other than for preventing or treating hypertension) for improving pregnancy and infant outcomes

Background Maternal nutrition during pregnancy is known to have an effect on fetal growth and development. It is recommended that women increase their calcium intake during pregnancy and lactation, although the recommended dosage varies among professionals. Currently, there is no consensus on the role of routine calcium supplementation for pregnant women other than for preventing or treating hypertension. Objectives To determine the effect of calcium supplementation on maternal, fetal and neonatal outcomes (other than for preventing or treating hypertension) as well as any possible side effects. Search strategy We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (17 March 2011). Selection criteria We considered all published, unpublished and ongoing randomised controlled trials (RCTs) comparing maternal, fetal and neonatal outcomes in pregnant women who received calcium supplementation versus placebo or no treatment. We excluded quasi-and pseudo-RCTs. Data collection and analysis Two review authors identified studies for inclusion and extracted the data. Two review authors performed data analysis. Main results This review includes data from 21 studies (involving 16,602 women). There were no statistically significant differences between women who received calcium supplementation and those who did not in terms of reducing preterm births (less than 37 weeks' gestation) (risk ratio (RR) 0.90; 95% confidence interval (CI) 0.73 to 1.11; 12 studies, 15615 women; random-effects model) and also in less than 34 weeks' gestation (RR 1.11; 95% CI 0.84 to 1.46; three trials, 5145 women). There was no significant difference in infant low birth weight between the two groups (RR 0.91; 95% CI 0.72 to 1.16; four trials, 13449 infants; random-effects). However, compared to the control group, women in the calcium supplementation group gave birth to slightly heavier birth weight infants (mean difference (MD) 64.66 g; 95% CI 15.75 to 113.58; 19 trials, 8287 women; random-effects). Authors' conclusions Calcium supplementation is associated with a significant protective benefit in the prevention of pre-eclampsia, and should be used for this indication according to a previous review. This review indicates that there are no additional benefits for calcium supplementation in prevention of preterm birth or low infant birth weight. While there was a statistically significant difference of 80 g identified in mean infant birth weight, there was significant heterogeneity identified, and the clinical significance of this difference is uncertain.