BackgroundVitamin D deficiency is particularly concerning in pregnant women, leading to various health-related issues in mothers and their babies, especially those born prematurely, including neonatal skeletal and respiratory disorders. In addition, there have been several reports indicating the presence of multiple impactful factors in the development of vitamin D deficiency. Therefore, we aimed to evaluate the vitamin D level in very preterm and moderately preterm newborns and investigate its association with presumed influential factors.MethodsThis cross-sectional descriptive study was performed on 54 mothers and their preterm neonates with gestational ages less than 34 weeks at delivery (i.e., very preterm and moderately preterm). After the serum vitamin D levels were determined from samples obtained in the first 24 h after birth, the babies were divided into two groups based on the presence or absence of deficiency. The relationship between several factors and the neonatal serum vitamin D level was investigated separately and in a linear step-wise regression model.ResultsThe differences between the groups regarding maternal age, gestational age, neonate's gender, birth weight, and delivery method with neonatal vitamin D levels were not statistically significant. However, maternal vitamin D levels strongly correlated with neonatal vitamin D levels (P-value < 0.001,r= 0.636). The regression model also yielded a strong predictive capability (P-value < 0.001, AdjustedR2= 0.606), with the maternal vitamin D level demonstrating a significant impact.ConclusionsLow vitamin D levels in pregnant mothers correlate with deficient levels in their preterm neonates. Therefore, as vitamin D deficiency significantly affects both the mother's and newborn's health, it is recommended that healthcare providers provide comprehensive plans for vitamin D supplementation during pregnancy.