Purpose: The association between maternal vitamin D concentrations and birth weight is controversial. We conducted a large-scale retrospective cohort study in southern China to explore this relationship.
Methods: From July 2017 to April 2019, we enrolled 10,586 pregnant women and measured serum vitamin D [via 25-hydroxyvitamin D, 25(OH)D] in the second trimester using electrochemiluminescence immunoassays. The association between macrosomia and 25(OH)D was analyzed using logistic regression and ROC curve.
Results: Average vitamin D concentration was 61.1 ± 20.2 nmol/L. Additionally, 31.1% participants had 25(OH)D concentrations <50.0 nmol/L, while 68.9% exhibited concentrations ≥50.0 nmol/L. Of the subjects, 3.2% of women delivered macrosomic infants (neonatal birth weight ≥4000 g) and 96.8% did not. The macrosomia group had lower vitamin D concentrations than the non-macrosomia group (59.5 ± 22.3 vs. 61.2 ± 20.1, p < .05). Approximately a third of each group had vitamin D < 50.0 nmol/L (non-macrosomia, 31.3%; macrosomia, 35.9%; p = .055). After adjusting for confounding variables, women with 25(OH)D ≥ 50.0 nmol/L had 24.3% lower macrosomia risk than women with 25(OH)D < 50.0 nmol/L (adjusted OR = 0.757, 95% CI = 0.599-0.956, p = .0193). The predictive accuracy of vitamin D concentrations for evaluating macrosomia risk was 0.667 area under the ROC curve.
Conclusion: Maternal vitamin D levels are negatively correlated with macrosomia. Elevating vitamin D above 50.0 nmol/L may reduce macrosomia incidence.
Keywords: Pregnancy; macrosomia; newborn; vitamin D deficiency; vitamin D sufficiency.