Effects of Vitamin D Supplementation During Pregnancy on Birth Size: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Nutrients. 2019 Feb 20;11(2):442. doi: 10.3390/nu11020442.


During pregnancy, vitamin D supplementation may be a feasible strategy to help prevent low birthweight (LBW) and small for gestational age (SGA) births. However, evidence from randomized controlled trials (RCTs) is inconclusive, probably due to heterogeneity in study design and type of intervention. A systematic literature search in the PubMed-Medline, EMBASE, and Cochrane Central Register of Controlled Trials databases was carried out to evaluate the effects of oral vitamin D supplementation during pregnancy on birthweight, birth length, head circumference, LBW, and SGA. The fixed-effects or random-effects models were used to calculate mean difference (MD), risk ratio (RR), and 95% Confidence Interval (CI). On a total of 13 RCTs, maternal vitamin D supplementation had a positive effect on birthweight (12 RCTs; MD = 103.17 g, 95% CI 62.29⁻144.04 g), length (6 RCTs; MD = 0.22 cm, 95% CI 0.11⁻0.33 cm), and head circumference (6 RCTs; MD:0.19 cm, 95% CI 0.13⁻0.24 cm). In line with these findings, we also demonstrated that maternal vitamin D supplementation reduced the risk of LBW (3 RCTs; RR = 0.40, 95% CI 0.22⁻0.74) and SGA (5 RCTS; RR = 0.69, 95% CI 0.51⁻0.92). The present systematic review and meta-analysis confirmed the well-established effect of maternal vitamin D supplementation on birth size. However, further research is required to better define risks and benefits associated with such interventions and the potential implications for public health.

Keywords: birth length; birthweight; diet; gestational age; head circumference; nutrition; pregnancy outcomes; vitamin D.

Publication types

  • Meta-Analysis
  • Systematic Review

MeSH terms

  • Birth Weight
  • Dietary Supplements*
  • Female
  • Humans
  • Infant, Low Birth Weight
  • Infant, Newborn
  • Infant, Small for Gestational Age
  • Male
  • Maternal Nutritional Physiological Phenomena*
  • Nutritional Status
  • Pregnancy
  • Pregnancy Complications / therapy
  • Pregnancy Outcome*
  • Prenatal Care / methods*
  • Randomized Controlled Trials as Topic
  • Treatment Outcome
  • Vitamin D / administration & dosage*
  • Vitamin D Deficiency / therapy


  • Vitamin D