The review found no eligible studies for this question.
Vitamin D + calcium supplementation may leads to higher preterm birth (less than 37 weeks' gestation) compared with placebo or no intervention (low certainty).
It is very uncertain whether vitamin D + calcium supplementation changes low birthweight (less than 2500 g) compared with placebo or no intervention (very low certainty).
Vitamin D + calcium supplementation probably leads to lower pre‐eclampsia compared with placebo or no intervention (moderate certainty).
It is very uncertain whether vitamin D + calcium supplementation changes gestational diabetes compared with placebo or no intervention (very low certainty).
The intervention may leads to lower pre‐eclampsia (low certainty).
The intervention may leads to lower preterm birth (low certainty).
The intervention leads to higher HELLP syndrome (high certainty).