Summary of findings 2. Supplementation with folate versus no intervention, placebo or other micronutrients without folate (maternal outcomes).
| Population: all women who become pregnant or were 12 or less weeks' pregnant at the time of the intervention Setting: the studies took place in nine high‐income countries and one low‐middle‐income country Intervention: supplementation with folate Comparison: no intervention, placebo or other micronutrients without folate | ||||||
| Outcomes | Anticipated absolute effects* (95% CI) | Relative effect (95% CI) | № of participants (studies) | Quality of the evidence (GRADE) | Comments | |
| Risk with no intervention, placebo or other micronutrients without folate | Risk with supplementation with folate | |||||
| Maternal anaemia at or near term (All) | Study population | not pooled | 0 (0 study) | No trial assessed this outcome. | ||
| not pooled | not pooled | |||||
| Maternal red blood cell folate at or near term (All) | not estimable | The mean maternal red blood cell folate at or near term (All) in the intervention group was 0 undefined more (0 more to 0 more) | not pooled | 0 (0 study) | No trial assessed this outcome. | |
| Serum folate at or near term | not estimable | not estimable | not pooled | 0 (0 study) | No trial assessed this outcome. | |
| Miscarriage (All) | Study population | RR 1.10 (0.94 to 1.28) | 7391 (5 RCTs) | ⊕⊕⊕⊝ moderate1 | ||
| 99 per 1000 | 109 per 1000 (93 to 127) | |||||
| Moderate | ||||||
| 96 per 1000 | 106 per 1000 (90 to 123) | |||||
| *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; RR: Risk ratio | ||||||
| GRADE Working Group grades of evidence High quality: We are very confident that the true effect lies close to that of the estimate of the effect Moderate quality: 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 quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect | ||||||
1 Most studies contributing data had design limitations (selection bias was unclear).