# The role of vitamin D deficiency in fetal growth restriction: a systematic review

## TL;DR

This paper reviews evidence linking low vitamin D levels in mothers to increased risk of poor fetal growth, but finds mixed results on whether vitamin D supplements help.

## Contribution

A systematic review showing consistent associations between maternal vitamin D deficiency and fetal growth restriction, while highlighting variability in supplementation trial outcomes.

## Key findings

- Low maternal 25(OH)D concentrations are consistently linked to increased risk of fetal growth restriction and small-for-gestational-age infants.
- Supplementation trial results are inconsistent due to differences in dosage, timing, and baseline vitamin D levels.
- Mechanistic studies support biological pathways through which vitamin D may influence placental and fetal development.

## Abstract

Fetal Growth Restriction (FGR) and Small-for-Gestational-Age (SGA) are major contributors to perinatal morbidity and mortality. Maternal vitamin D deficiency has been proposed to impair placental development and fetal growth through mechanisms involving angiogenesis, immune regulation, and oxidative stress. Increasing evidence suggests that maternal 25-hydroxyvitamin D [25(OH)D] status may play a significant role in the pathogenesis of impaired fetal growth.

To synthesize evidence on the association between maternal 25-hydroxyvitamin D [25(OH)D] concentrations and the risk of FGR and SGA, and to evaluate the impact of vitamin D supplementation on fetal growth outcomes.

A systematic search of PubMed, Cochrane Library, Springer, ScienceDirect, and DOAJ was performed following PRISMA 2020 guidelines. Observational studies and randomized controlled trials examining maternal vitamin D status and fetal growth outcomes were included.

The 48 included studies showed consistent evidence linking low maternal 25(OH)D concentrations with increased risk of FGR and SGA, with several analyses demonstrating dose–response patterns at lower vitamin D thresholds. Associations with preterm birth were directionally similar but less consistent. Findings from intervention trials assessing vitamin D supplementation were heterogeneous, influenced by variations in dosage, timing of initiation, baseline vitamin D status, adherence, and co-nutrient exposures. Experimental and mechanistic studies further supported biological plausibility, demonstrating vitamin D–mediated effects on placental angiogenesis, immune modulation, endocrine signaling, and oxidative stress pathways.

Maternal vitamin D deficiency is consistently associated with impaired fetal growth, although findings from supplementation trials remain variable. Standardized dosing strategies, harmonized diagnostic cut-offs, and better-controlled interventions are needed to clarify the optimal role of vitamin D in preventing FGR and SGA.

https://www.crd.york.ac.uk/prospero/, identifier CRD42024622395.