Maternal vitamin D status, prolonged labor, cesarean delivery 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 to 1966). we used labor and delivery data to classify cases of adverse outcomes.result:twenty-four percent of women were vitamin d deficient (25(oh)d <30 nmol l−1), 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 body mass index, 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.