Association between serum 25-hydroxyvitamin D [25(OH)D] levels and vaginal delivery in pregnant women: an observational case–control study from Türkiye

Objective This study aimed to evaluate the relationship between maternal serum 25-hydroxyvitamin D [25(OH)D] levels and the likelihood of vaginal delivery. Materials and methods This observational case–control study was conducted with a total of 298 women, comprising a case group of those who were unable to deliver vaginally and underwent emergency cesarean section ( n = 49), and a control group of those who delivered vaginally ( n = 249). The study data were collected using a questionnaire developed in line with the relevant literature. To explore the effects of independent variables on the dependent variable, both univariate and multivariate logistic regression analyses were performed. Results According to the findings of our study, higher serum 25(OH)D levels were significantly associated with a reduced risk of cesarean delivery ( β = −0.369, p = 0.001). Specifically, each 1 ng/mL increase in serum 25(OH)D levels reduces the risk of cesarean delivery by approximately 30.8% [Exp( β ) = 0.692, 95% CI = 0.611–0.783]. On the other hand, a high body mass index (BMI) pre-pregnancy and at the time of delivery, excessive gestational weight gain, and the presence of chronic diseases were associated with a higher risk of cesarean delivery ( p < 0.05). In addition, giving birth at a later gestational week was found to be associated with a higher rate of vaginal delivery ( p < 0.05). No significant associations were found between the mode of delivery and maternal age, total number of pregnancies, previous vaginal delivery, pre-pregnancy family planning method, neonatal birth weight, the total number of non-stress tests (NSTs) performed during pregnancy, or the number of antenatal physician visits ( p > 0.05). Conclusion Higher serum vitamin D levels were associated with an increased likelihood of vaginal delivery. In this context, optimizing vitamin D status through sunlight exposure, nutrition, or supplementation may represent an important step in protecting maternal and neonatal health.