Summary of findings 2. Vitamin D + calcium supplementation compared to placebo or no intervention for pregnancy and neonatal health outcomes.
| Vitamin D + calcium supplementation compared to placebo/control for pregnancy and neonatal health outcomes | |||||||
| Patient or population: pregnant women and their infants.. Setting: trials were carried from 1980s to 2015 in countries from Iran, India, and Brazil. Only the study in Brazil was within the tropics. Most did not report the season in which it was carried out or it was mixed. Intervention: vitamin D + calcium supplementation. Comparison: placebo/control. | |||||||
| Outcomes | Anticipated absolute effects* (95% CI) | Relative effect (95% CI) | № of participants (studies) | Certainty of the evidence (GRADE) | Comments | ||
| Risk with placebo/control | Risk with vitamin D + calcium supplementation | ||||||
| Pre‐eclampsia | Study population | RR 0.50 (0.32 to 0.78) | 1174 (4 RCTs) | ⊕⊕⊕⊝ MODERATE1 | Included trials: Asemi 2012; Marya 1987; Samimi 2016; Taherian 2002 | ||
| 94 per 1000 | 47 per 1000 (30 to 73) | ||||||
| Gestational diabetes | Study population | RR 0.33 (0.01 to 7.84) | 54 (1 RCT) | ⊕⊝⊝⊝ VERY LOW2,3 | Included trial: Asemi 2012 | ||
| 37 per 1000 | 12 per 1000 (0 to 290) | ||||||
| Maternal adverse events | ‐ | ‐ | ‐ | ‐ | ‐ | No trials reported on this outcome | |
| Preterm birth (less than 37 weeks' gestation) | Study population | RR 1.52 (1.01 to 2.28) | 942 (5 RCTs) | ⊕⊕⊝⊝ LOW4,5 | Included trials: Asemi 2012; Diogenes 2013, Mirghafourvand 2013, Samimi 2016; Taherian 2002; | ||
| 72 per 1000 | 110 per 1000 (73 to 165) | ||||||
| Low birthweight (less than 2500 g) | Study population | RR 0.68 (0.10 to 4.55) | 110 (2 RCTs) | ⊕⊝⊝⊝ VERY LOW6,7 | Included trials: Diogenes 2013; Samimi 2016 | ||
| 59 per 1000 | 40 per 1000 (6 to 268) | ||||||
| *The risk in the intervention group (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; RCT: randomised controlled trial; RR: Risk ratio | |||||||
| GRADE Working Group grades of evidence High certainty: We are very confident that the true effect lies close to that of the estimate of the effect Moderate certainty: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different Low certainty: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect Very low certainty: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect | |||||||
1 We downgraded (1) level for serious limitations in study design due to one study being at high risk of attrition and selection bias and three studies being at high risk of performance and detection bias.
2 We downgraded (1) level for serious limitations in study design due to one study being at high risk of performance and detection bias.
3 We downgraded (2) levels for very serious limitations in imprecision due to one small study, with a single event and wide 95% confidence intervals (CI) crossing the line of no effect contributing data.
4 We downgraded (1) level for serious limitations in study design due to three studies being at unclear risk of allocation concealment and three studies being at high risk of performance and detection bias.
5 We downgraded (1) level for serious limitations in imprecision due to wide 95% confidence intervals (CI).
6 We downgraded (1) level for serious limitations in study design due to one study being at unclear risk of allocation concealment and one study being at high risk of attrition bias.
7 We downgraded (2) levels for very serious limitations in imprecision due two small studies, with very few events and wide 95% confidence intervals (CI) crossing the line of no effect contributing data.