Maternal vitamin D status, prolonged labor, and cesarean and instrumental delivery in an era with a low cesarean rate

OBJECTIVE: To examine the association between maternal 25-hydroxyvitamin D (25(OH)D) and adverse labor and delivery outcomes. STUDY DESIGN: We measured serum 25(OH)D at ≤26 weeks gestation in a random subsample of vertex, singleton pregnancies in women who labored (n=2798) from the 12 site Collaborative Perinatal Project (1959–66). We used labor and delivery data to classify cases of adverse outcomes. RESULTS: Twenty-four percent of women were vitamin D deficient (25(OH)D <30 nmol/L) and 4.5%, 3.3%, 1.9%, and 7.5% of women had prolonged stage 1 labor, prolonged stage 2 labor, primary cesarean delivery, or indicated instrumental delivery, respectively. After adjustment for prepregnancy BMI, race, and study site, 25(OH)D concentrations were not associated with risk of prolonged stage 1 or 2, cesarean delivery, or instrumental delivery. CONCLUSION: Maternal vitamin D status at ≤26 weeks was not associated with risk of prolonged labor or operative delivery in an era with a low cesarean rate.