Serum Vitamin D Levels in Pregnant Women: The Role of Supplementation on Preterm Infant Outcomes.

OBJECTIVE: Vitamin D plays a crucial role in maternal and infant health. This study was aimed at evaluating and comparing serum vitamin D levels and clinical outcomes between preterm mothers who received vitamin D supplements and those who did not. METHODS: In a cross-sectional study, a total of 328 women were enrolled, of whom 310 mother-infant pairs were included in the final analysis. The supplementation group consisted of mothers who consumed at least 1000 international units of vitamin D daily for a minimum of 1 month prior to delivery. Clinical characteristics and neonatal outcomes were compared between the supplementation and nonsupplementation cohorts. RESULTS: The mean serum vitamin D levels were significantly higher in the supplementation group for both mothers (23.88 ± 15.66 vs. 12.68 ± 7.37 ng/mL) and their infants (17.55 ± 12.23 vs. 10.38 ± 7.35 ng/mL; p <0.001 for both). Infants in the nonsupplementation group required resuscitation in the delivery room significantly more often (p = 0.019). Furthermore, the incidence of respiratory distress syndrome (p = 0.002) and respiratory problems (p = 0.004) were significantly higher in the nonsupplemented group. No statistically significant differences were observed regarding one- and fifth-minute Apgar scores (p = 0.200 and p = 0.117), birth weight (p = 0.343), or neonatal mortality (p = 0.062). CONCLUSIONS: Maternal vitamin D supplementation is associated with higher serum vitamin D levels in both mothers and preterm infants, as well as a reduced prevalence of adverse neonatal respiratory outcomes. These findings underscore the clinical importance of prenatal vitamin D supplementation to promote maternal and neonatal health, particularly in populations with high rates of vitamin D deficiency.