Impact of First-Trimester Vitamin D Levels on Pregnancy Complications

Vitamin D Levels and Pregnancy Complications

Abstract

Objective: Vitamin D deficiency during pregnancy is a global health issue, affecting a significant portion of pregnant women. It has been linked to various adverse maternal and fetal outcomes, yet studies offer conflicting results on its direct impact. This study aimed to evaluate the prevalence of vitamin D deficiency in the first trimester and its association with pregnancy complications.
Methods: This retrospective cohort study involved 1,999 pregnant women who attended Gazi University’s Obstetrics and Gynecology Clinic and had their vitamin D levels measured during the first trimester between January 2018 and August 2023. Exclusions included incomplete data, multiple pregnancies, and significant comorbidities. Participants were categorized into four groups based on their vitamin D levels, and associations with fetal and adverse pregnancy outcomes
Results: When we grouped pregnant women according to their vitamin D levels, 36.3% were severely deficient (<10 ng/mL), 47.5% were deficient (10–19 ng/mL), and 13.1% were insufficient (20–30 ng/mL). Only 63 (3.2%) pregnant women had sufficient vitamin D levels (>30 ng/mL). A significant correlation was found between vitamin D levels and age, with older women showing higher levels (p < 0.001). There was no clear relationship between vitamin D levels and other pregnancy complications, such as preeclampsia, gestational diabetes, preterm labor, or adverse neonatal outcomes. The incidence of abortion in women with vitamin D levels >30 ng/mL was 18%, which was significantly higher than in lower vitamin D groups (p = 0.029). Vitamin D levels were significantly lower in pregnancies with term birth weight below 2500 grams (p = 0.024).
Conclusion: Our study confirms a high prevalence of vitamin D deficiency among women in the first trimester of pregnancy and shows that vitamin D levels increase with advancing maternal age. Low vitamin D levels were not associated with adverse pregnancy outcomes.