A NEW study suggests that low vitamin D levels in the first trimester of pregnancy are associated with a significantly higher risk of preterm birth and decreased foetal growth. The findings highlight the importance of early pregnancy nutrition and may prompt reconsideration of routine vitamin D testing in prenatal care.
The study, led by researchers from Pennsylvania State University, analysed data from 351 pregnant women in the U.S. as part of the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be. Serum 25-hydroxyvitamin D levels were measured between 6 and 13 weeks and again at 16 to 21 weeks of gestation. Researchers also tracked foetal growth through ultrasound and assessed neonatal measurements at birth.
The results revealed that one in five women had vitamin D insufficiency (less than 50 nmol/L) during the first trimester. Notably, women with vitamin D levels below 40 nmol/L were more than four times as likely to give birth prematurely compared to those with levels of 80 nmol/L or greater. Furthermore, for every 10 nmol/L increase in first-trimester vitamin D levels, foetal length improved, reinforcing the nutrient’s role in early foetal development.
In contrast, vitamin D levels in the second trimester showed no significant impact on foetal growth or pregnancy outcomes. This suggests that early pregnancy may be a critical window for ensuring adequate vitamin D levels.
Study author Alison Gernand, PhD, MPH, RD, emphasised that vitamin D testing is not currently a standard part of prenatal care in the U.S. but suggested that healthcare providers discuss dietary sources and supplementation with expectant mothers early in pregnancy.
While the study was observational and had a relatively small sample size for preterm births, the strong association between early vitamin D insufficiency and adverse pregnancy outcomes underscores the need for further research. Future studies should track vitamin D levels before conception and throughout pregnancy to determine whether supplementation could mitigate these risks.
Aleksandra Zurowska, EMJ
Reference
Wagner A. Vitamin D matters during first trimester, researchers find. Available at : www.psu.edu/news/health-and-human-development/story/vitamin-d-matters-during-first-trimester-researchers-find. Last accessed: 28 February 2025.
