PubMedThe Cochrane database of systematic reviews2026-11-11
Regimens of vitamin D supplementation for women during pregnancy.
Trak-Fellermeier Maria Angelica MA, Palma Molina Ximena E XE, Huey Samantha L SL, Salisi James A JA et al.
Vitamin D deficiency is common in pregnancy and has been associated with adverse health outcomes for the mother and infant, including pre-eclampsia, gestational diabetes, preterm birth, and low birthweight. The World Health Organization (WHO) recommends a vitamin D intake of 200 international units (IU) per day during pregnancy. Vitamin D supplementation is recommended for women with suspected vitamin D deficiency, but it is not universally recommended. The effects of different doses (regimens) of vitamin D during pregnancy have not been established. This is an update of a Cochrane review first published in 2019, which concluded that vitamin D supplementation (at any dose) may have little or no beneficial effects on maternal or neonatal outcomes.
To assess the effects of different doses of vitamin D supplementation (alone or in combination with calcium or other micronutrients) during pregnancy: more than 600 IU/day versus up to 600 IU/day, and 4000 IU/day or more versus less than 4000 IU/day.
We searched the Cochrane Central Register of Controlled Trials (CENTRAL), ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform, and relevant databases in April 2026.
We included randomised trials evaluating the effects of different vitamin D regimens during pregnancy on maternal and infant health outcomes. Trials of pregnant women with pre-existing conditions or multiple pregnancies were excluded.
The critical maternal outcomes were pre-eclampsia, gestational diabetes, and any adverse events. The critical infant outcomes were preterm birth and low birthweight.
We used the Cochrane RoB 1 tool to independently assess the risk of bias in included studies.
Two review authors independently assessed study eligibility and extracted data from included studies. We conducted fixed-effect meta-analyses in RevMan where it was reasonable to assume that studies were estimating the same underlying treatment effect. If substantial heterogeneity was detected, we conducted random-effects meta-analyses, using the Mantel-Haenszel method for dichotomous outcomes and inverse-variance method for continuous outcomes. We used the GRADE approach to assess the certainty of the evidence.
This review update included 25 studies with 7008 pregnant women. The included studies were conducted in 14 countries between 2004 and 2024. We excluded 29 studies, identified 23 ongoing studies, and listed 21 studies as awaiting classification.
The overall risk of bias of the 25 included studies was mixed. The certainty of the evidence was low for most critical outcomes due to serious risk of bias and imprecision in the results. Vitamin D at a dose of more than 600 IU/day versus up to 600 IU/day, alone or in combination with other micronutrients (19 studies, 5141 women) Vitamin D supplementation during pregnancy at doses of more than 600 IU/day, compared with up to 600 IU/day, may make little or no difference to the risk of pre-eclampsia (risk ratio (RR) 0.90, 95% confidence interval (CI) 0.65 to 1.25; 8 studies, 2629 women; low-certainty evidence), gestational diabetes (RR 0.85, 95% CI 0.52 to 1.40; 6 studies, 2373 women; low-certainty evidence), preterm birth (RR 1.02, 95% CI 0.78 to 1.32; 7 studies, 3411 women; low-certainty evidence), or low birthweight (RR 0.90, 95% CI 0.71 to 1.14; 6 studies, 2090 women; low-certainty evidence). Vitamin D at a dose of 4000 IU/day or more versus less than 4000 IU/day, alone or in combination with other micronutrients (14 studies, 4954 women) Vitamin D supplementation during pregnancy at doses of 4000 IU/day or more, compared with less than 4000 IU/day, may make little or no difference to the risk of pre-eclampsia (RR 0.90, 95% CI 0.65 to 1.25; 5 studies, 2456 women; low-certainty evidence), gestational diabetes (RR 0.86, 95% CI 0.55 to 1.35; 5 studies, 2420 women; low-certainty evidence), or preterm birth (RR 0.97, 95% CI 0.79 to 1.19; 7 studies, 3409 women; low-certainty evidence), and probably makes little or no difference to the risk of low birthweight (RR 0.96, 95% CI 0.76 to 1.21; 3 studies, 1637 women; moderate-certainty evidence). Adverse events in both comparisons Reporting of adverse events (e.g. hypercalcaemia, hypervitaminosis D) was heterogeneous across studies. Few adverse events were reported, and we observed no differences between groups (low-certainty to moderate-certainty evidence).
Vitamin D supplementation during pregnancy at higher versus lower doses may make little or no difference to the risk of pre-eclampsia, gestational diabetes, preterm birth, or low birthweight. Future research should prioritise adequately powered trials with harmonised study designs that include more women from under-represented regions and focus on a consistently defined set of maternal and infant health outcomes. Additionally, trials should include longer follow-up to assess infant and child health outcomes beyond birth.
This Cochrane review had no dedicated funding.
The previous version of this review was published in 2019 (DOI 10.1002/14651858.CD013446). The original protocol for this review was registered with PROSPERO (https://www.crd.york.ac.uk/PROSPERO/view/CRD42018103763).