Vitamin D supplement in pregnancy: dose and recommendations, a systematic review

ABSTRACT

Objective. This systematic review synthesises evidence from randomised controlled trials (RCTs) on the safety, efficacy, and optimal dosing of vitamin D supplementation during pregnancy.

Materials and Methods. The present study is an integrative review of literature based on clinical trials published in journals indexed in the PubMed databases and the Cochrane Library. A comprehensive search was conducted in PubMed and the Cochrane Library until May 2024. We included RCTs evaluating vitamin D supplementation in pregnant women, focusing on maternal and neonatal outcomes and dosing strategies. A total of 64 RCTs were thematically synthesised using PRISMA guidelines.

Results. Evidence from 64 RCTs indicates that vitamin D supplementation is associated with improved maternal 25(OH) D levels, especially when administered at daily doses of ≥2000 IU. Supplementation of 4000 IU/day was found to be safe and most effective in achieving maternal and neonatal sufficiency. Higher intermittent doses (e.g., 50,000 IU every two weeks) also showed safety and improved metabolic profiles in some populations. While supplementation did not consistently reduce preeclampsia or gestational diabetes mellitus, it was associated with a lower risk of atopic eczema in offspring during the first year of life and improved bone mineralisation in children up to six years of age.

Conclusions. Vitamin D supplementation during pregnancy is safe and effective in correcting deficiency, particularly at doses ≥2000 IU/day. Although clinical benefits on major obstetric outcomes remain inconsistent, supplementation may offer advantages in select populations. Defining baseline vitamin D status, ethnicity, and timing of supplementation remains crucial when determining optimal dosing strategies.