Vitamin D-Related risk factors for preterm and full-term infants at birth: A retrospective study in Wuxi, China

Background/Objectives: Vitamin D is thought to play a role in early immune development of infants. However, national data on vitamin D status in newborns is limited in China. We aimed to evaluate the vitamin D status in preterm and full-term neonates and its influencing factors in Wuxi, southeastern China. Subjects/Methods: 813 infants born were recruited in this study from May 2020 to May 2022, including 167 very preterm (< 32 ^+ 0 weeks), 454 preterm (32 ^+ 0 -36 ^+ 6 weeks) and 192 full-term (≥ 37 ^+ 0 weeks) newborns. The umbilical cord serum level of 25-hydroxyvitamin D (25(OH)D) was measured. Results The median level of serum 25(OH)D was 35.9 nmol/L, and 82.7% of them were vitamin D deficient. The serum 25(OH)D level was lower in full-term infants compared with preterm and very preterm infants at birth, while there was no significant difference (preterm, 95% confidence interval [CI], 0.484, 1.657, p = 0.725; very preterm, 95% CI, 0.434, 2.061, p = 0.946) in the prevalence of vitamin D deficiency among them. It was found that vitamin D deficiency in newborns was significantly associated with season of birth (Spring, 95% CI, 0.128,0.541, p < 0.001; Summer, 95% CI, 0.101, 0.491, p < 0.001; Autumn, 95% CI, 0.106, 0.465, p < 0.001) and maternal pre-pregnancy BMI (< 25 kg/m ² , 95% CI, 0.150, 0.514, p < 0.001; 25–30 kg/m ² , 95% CI, 0.277, 0.916, p = 0.025) after controlling for maternal age, birth weight and gestational age. Conclusions : More attentions should be focused on the nutritional vitamin D status of infants born in winter. Infants born to women who are obese before pregnancy are likely to have greater odds of vitamin D deficiency at birth which requires urgent attentions. Adequate daily vitamin D supplementation for newborns is recommended and warranted immediately after birth.