Maternal vitamin D status and preterm birth: an eight-year retrospective cohort study in the Southeastern United...

Investigate the association between vitamin D status (as measured by 25-hydroxyvitamin D concentration [25(OH)D]) and gestational age at delivery.

This was a retrospective chart review of electronic medical records (n = 15,506) from women delivering at the Medical University of South Carolina, with first maternal 25(OH)D concentrations measured from January 2016 to March 2024.

Women delivering <37 weeks (n = 1652; 31.3 ± 17.8 ng/mL) had lower 25(OH)D concentrations compared to those delivering at 37 weeks or later (n = 13,451; 34.8 ± 17.3 ng/mL), with a mean difference of -3.46 ng/mL (95% Confidence Interval (CI): -4.54 to -2.38, p < 0.0001). This difference was even more pronounced among women delivering before 32 weeks (n = 385; 26.2 ± 14.9 ng/mL), who had substantially lower 25(OH)D concentrations than term deliveries, with a mean difference of -8.56 ng/mL (95% CI: -10.70 to -6.42, p < 0.0001).

Maternal vitamin D status was associated with gestational age at delivery. Lower maternal 25(OH)D concentrations were observed among women who delivered preterm compared with those delivering at term. These findings suggest a potential relationship between vitamin D status and preterm birth and support further research into whether optimizing vitamin D status during pregnancy may improve perinatal outcomes.