A Cochrane review «Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems»1 «Hofmeyr GJ, Lawrie TA, Atallah ÁN et al. Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems. Cochrane Database Syst Rev 2018;(10):CD001059. .»1 included 27 studies, all of good quality, with a total of 18 064 women. With calcium supplementation (1g or over/day) compared to placebo, the risk of high blood pressure (RR 0.65, 95% CI 0.53 to 0.81, statistical heterogeneity I2=74%; 12 trials, n=15 470) and the risk of pre-eclampsia (RR 0.45, 95% CI 0.31 to 0.65, statistical heterogeneity I2=70%; 13 trials, n=15 730) were reduced. The effect was greatest for high-risk women (RR 0.22, 95% CI 0.12 to 0.42; 5 trials, n=587), and those with low baseline calcium intake (RR 0.36, 95% CI 0.20 to 0.65, statistical heterogeneity I2=76%; 8 trials, 10 678 women).
The average risk of preterm birth was reduced in the calcium group overall (RR 0.76, 95% CI 0.60 to 0.97; statistical heterogeneity I2=60%; 11 trials, n=15 275) and amongst women at high risk of developing pre-eclampsia recruited to four small trials (RR 0.45, 95% CI 0.24 to 0.83; n=568). There was no overall effect on the risk of stillbirth or death before discharge from hospital (RR 0.90, 95% CI 0.74 to 1.09; 11 trials, 15 665 babies). The composite outcome maternal death or serious morbidity was reduced (RR 0.80, 0.65 to 0.97; 4 trials, n=9 732). Most of the women in these trials were low risk and had a low calcium diet. Maternal deaths were reported in only one trial. One death occurred in the calcium group and six in the placebo group, a difference which was not statistically significant (RR 0.17, 95% CI 0.02 to 1.39).
Comment: The quality of evidence is downgraded by inconsistency (variability in results across studies).
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