Any vitamin E supplementation showed no clear difference in stillbirth compared with placebo, no placebo or other supplements (moderate certainty).
Any vitamin E supplementation showed no clear difference in preterm birth (less than 37 weeks' gestation) compared with placebo, no placebo or other supplements (high certainty).
Any vitamin E supplementation showed no clear difference in clinical pre‐eclampsia (random‐effects model) compared with placebo, no placebo or other supplements (moderate certainty).
Any vitamin E supplementation showed no clear difference in intrauterine growth restriction (various definitions) compared with placebo, no placebo or other supplements (high certainty).
Any vitamin E supplementation showed no clear difference in prelabour rupture of fetal membranes ‐ preterm compared with placebo, no placebo or other supplements (low certainty).
Any vitamin E supplementation leads to lower bleeding episodes (placental abruption) compared with placebo, no placebo or other supplements (high certainty).
It is very uncertain whether summary of findings table ‐ Vitamin B12 supplementation changes maternal vitamin B12 deficiency compared with placebo/no vitamin B12 supplementation (very low certainty).
Vitamin D supplementation probably leads to lower pre‐eclampsia compared with placebo or no intervention (moderate certainty).
Vitamin D supplementation probably leads to lower gestational diabetes compared with placebo or no intervention (moderate certainty).
Vitamin D supplementation may leads to lower maternal adverse events: severe postpartum haemorrhage compared with placebo or no intervention (low certainty).
It is very uncertain whether vitamin D supplementation changes maternal adverse event: nephritic syndrome compared with placebo or no intervention (very low certainty).
Vitamin D supplementation showed no clear difference in preterm birth (less than 37 weeks' gestation) compared with placebo or no intervention (low certainty).
Vitamin D supplementation probably leads to lower low birthweight (less than 2500 g) compared with placebo or no intervention (moderate certainty).
It is very uncertain whether summary of findings table ‐ Vitamin B12 supplementation changes maternal anaemia compared with placebo/no vitamin B12 supplementation (very low certainty).
Summary of findings table ‐ Vitamin B12 supplementation showed no clear difference in low birthweight (< 2500 g) compared with placebo/no vitamin B12 supplementation (low certainty).
Summary of findings table ‐ Vitamin B12 supplementation showed no clear difference in preterm birth (< 37 weeks) compared with placebo/no vitamin B12 supplementation (low certainty).
The review found no eligible studies for this question.