Association of Maternal Serum 25-hydroxyvitamin D Concentrations in Second Trimester with Delivery Mode in A Chinese Population

Objective: To determine the maternal serum 25-hydroxyvitamin D [25(OH)D] concentrations in a Chinese population and investigate its associations with subsequent delivery mode by studying 1924 unrelated pregnant women. Methods: The serum 25(OH)D concentrations was measured by euzymelinked immunosorbent assay (ELISA). Simultaneously, maternal information and subsequent delivery mode were collected. Logistic regression analysis was performed to assess the associations between 25(OH)D concentrations and caesarean section. Results: The median (IQR) serum concentration of 25(OH)D for the total subjects was 43.4 (35.2-56.9) nmol/L. Among them, 1225 (63.7%) women were in the status of 25(OH)D deficiency (< 50.0 nmol/L). The 25(OH)D concentrations showed significant variation by body mass index (BMI), parity and season of sampling. Women with caesarean section was older, and with higher BMI and rate of abnormal pregnancy history, suggesting advanced age, obesity and abnormal pregnancy history may be the risk factors for the subsequent caesarean section. Compared with 25(OH)D from 50.0 to 74.9 nmol/L, women with low 25(OH)D concentrations (< 50.0 nmol/L) was not significantly associated with caesarean section. Only in the subgroup of the women without abnormal pregnancy history, higher 25(OH)D (> 75.0 nmol/L) concentrations could significantly decrease the risk of caesarean section. Conclusion: Vitamin D deficiency is a quite serious problem in Chinese pregnant women. There is no evidence that the maternal serum 25(OH)D concentrations is associated with increased risk of caesarean section.