Is There a Relationship Between the Vitamin D Status of Newborns and Their Mothers and the Occurrence of Physiological and Out of Physiological Hyperbilirubinemia? A Case-Control Study

Background: The role of vitamin D deficiency in the severity of neonatal hyperbilirubinemia (NH) has been speculative. There are controversies about the association of NH and vitamin D status in neonates and their mothers Objectives: To evaluate the relationship between physiological and out of physiological NH and the vitamin D status of both neonates and their mothers. Methods: This case-control study was conducted with 50 mothers and their healthy term newborns (born after 37 weeks of gestation) with non-physiological NH (case group) and 150 mothers and their healthy term newborns with physiological NH (control group) in Golestal Hospital Tehran, Iran from October 2020 to June 2024. The relationship between the vitamin D status of newborns and mothers and the newborns’ bilirubin levels was defined as the main outcome measures. Blood samples were collected from the subjects between the 3rd-5th days postpartum to measure bilirubin and vitamin D levels. The data was analyzed using a Multivariate logistic Regression analysis to estimate OR at a 95% CI. Results: The neonates and mothers in the case group exhibited significantly lower vitamin D levels compared to those in the control group (27.8 ± 10.04 ng/mL vs. 33.9 ± 9.39 ng/mL, P = 0.006 and 20.56 ± 10.2 ng/mL vs. 26 ± 8.92 ng/mL, P = 0.001, respectively). A significant correlation was observed between neonatal and maternal vitamin D levels in the case and control groups (r = 0.74, P = 0.01 and r = 0.77, P = 0.01, respectively). Moreover, a significant negative correlation was found between the newborns’ bilirubin levels and both neonatal and maternal vitamin D status in the case group (r = -0.34, P = 0.02 and r = -0.21, P = 0.04, respectively). Additionally, a significant negative correlation was observed between the newborns’ bilirubin levels and both neonatal and maternal vitamin D status in the control group (r = -0.41, P = 0.01 and r = -0.42, P = 0.01, respectively). Conclusions: Vitamin D levels were significantly lower in neonates with non-physiological NH, compared to those with physiological NH. Moreover, a significant negative correlation was observed between the newborns’ bilirubin levels and both neonatal and maternal vitamin D status. This correlation was more pronounced in cases of non-physiological NH. It appears that vitamin D levels play a role in NH.