Summary of findings for the main comparison. Calcium supplementation versus placebo or no treatment (maternal outcomes) for preventing or treating hypertension) for improving pregnancy and infant outcomes.
| Calcium supplementation versus placebo or no treatment for improving pregnancy and infant outcomes | ||||||
| Patient or population: healthy pregnant women receiving calcium supplementation vs placebo or no treatment Settings: trials located in Australia, Guatemala, India (3), Iran, and the USA (3). A multi‐centre study took place in Argentina, Egypt, India, Peru, South Africa, United Kingdom and Vietnam. Intervention: calcium supplementation versus placebo or no treatment (maternal outcomes) | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect (95% CI) | No of Participants (studies) | Quality of the evidence (GRADE) | Comments | |
| Assumed risk | Corresponding risk | |||||
| Control | Calcium supplementation versus placebo or no treatment (maternal outcomes) | |||||
| Preterm birth (a) Birth prior to 37 weeks | Study population | RR 0.86 (0.7 to 1.05) | 16139 (13 studies) | ⊕⊕⊕⊝ moderate1 | We conducted sensitivity analysis by removing 2 trials with unclear risk of bias for allocation concealment; the results then favoured treatment with calcium supplementation (RR 0.80, 95% CI 0.65 to 0.99; 11 trials, 15379 women). | |
| 105 per 1000 | 90 per 1000 (73 to 110) | |||||
| Moderate | ||||||
| 100 per 1000 | 86 per 1000 (70 to 105) | |||||
| Preterm birth (b) Birth prior to 34 weeks | Study population | RR 1.04 (0.8 to 1.36) | 5669 (4 studies) | ⊕⊕⊕⊝ moderate1 | ||
| 36 per 1000 | 38 per 1000 (29 to 49) | |||||
| Moderate | ||||||
| 30 per 1000 | 31 per 1000 (24 to 41) | |||||
| Low birthweight (< 2500 g) | Study population | RR 0.93 (0.81 to 1.07) | 14162 (6 studies) | ⊕⊕⊕⊝ moderate2 | ||
| 116 per 1000 | 108 per 1000 (94 to 125) | |||||
| Moderate | ||||||
| 86 per 1000 | 80 per 1000 (70 to 92) | |||||
| *The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: Confidence interval; RR: Risk ratio; | ||||||
| GRADE Working Group grades of evidence High quality: Further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: We are very uncertain about the estimate. | ||||||
1 Wide confidence interval crossing the line of no effect. (‐1) 2 Statistical heterogeneity (I2 > 60%). (‐1)