Vitamin D intake and preterm birth: A systematic review
More details
Hide details
Department of Midwifery, School of Health & Care Sciences, University of West Attica, Athens, Greece
Publication date: 2023-10-24
Corresponding author
Artemisia Kokkinari   

Department of Midwifery, School of Health & Care Sciences, University of West Attica, Athens, Greece
Eur J Midwifery 2023;7(Supplement 1):A163
Several studies suggest an association between vitamin D deficiency (VDD) and preterm birth (PTB). Most seemed to concur that mothers who delivered preterm infants had lower 25 hydroxyvitamin D (25(OH)D) concentrations compared to women who delivered full term infants, while others focused on the role of vitamin D in the prevention of PTB.

Material and Methods:
We searched the PubMed, Google Scholar, Web of Science, Science Direct, Embase, Cochrane, Crossref, and CAS databases for systematic reviews (SRs) of randomized controlled trials (RCTs) and observational studies published from 2016 to 2021. These concerned the association of PTB with maternal 25(OH)D levels, at different gestational ages, with or without vitamin D supplementation or in combination with other vitamins or minerals. We used a measurement tool to assess systematic reviews (AMSTAR), which rated the quality of each SR as low, average or high.

The literature review revealed an association of VDD with prematurity, at values less than 30 ng/dl. Maternal 25(OH)D levels of <30 ng/dl had a greatly increased risk of PTB at a gestational age (GA) of <32-34 weeks. Generally, the risk of PTB was significantly reduced when maternal serum 25(OH)D concentrations were ≥40 ng/dl. In particular, 25(OH)D <20 ng/dl levels, in the second trimester of pregnancy, had an increased risk of preterm delivery. Vitamin D supplementation has been suggested as an intervention to protect against the risk of PTB. Vitamin D supplementation in pregnancy was associated with a reduced risk of PTB compared with no intervention or placebo. When vitamin D supplementation was administered to achieve a 25(OH)D concentration of >40 ng/ml, there was a lower risk of PTB. In high-risk pregnancies, as serum 25(OH)D levels increased, so did GA. The existing evidence regarding universal, preventive vitamin D administration as part of antenatal care to improve adverse pregnancy outcomes and the risk of PTB remains unclear.

In conclusion, taking vitamin D during pregnancy to prevent PTB is controversial and the actual benefits unclear. Further RCTs are needed.

VDD, vitamin D deficiency; PTB, preterm birth; 25(OH)D, 25 hydroxyvitamin D; SRs, systematic reviews; RCTs, randomized controlled trials; AMSTAR, measurement tool to assess systematic reviews; GA, gestational age;
The authors have no conflicts of interest to disclose.
This research received no external funding.
AK conceived the topic; AK, MD and GI retrieved the literature; AK wrote the paper; KB collected the results of the values of 25(OH)D; MD, AL, VV and GI provided relevant methodological support and supervision. All authors contributed to editorial changes in the manuscript. All authors read and approved the final manuscript.
Journals System - logo
Scroll to top