Influent factors of gestational vitamin D deficiency and its relation to an increased risk of preterm delivery in Chinese population.

Gestational vitamin D deficiency (VDD) has been linked with adverse pregnant outcomes. To investigate influent factors of gestational VDD and its relation to the incidence of preterm delivery, total 3598 eligible mother-and-singleton-offspring pairs were recruited. For serum 25(OH)D concentration, 941 pregnant women were sufficient, 1260 insufficient, and 1397 deficient. Further analysis showed that VDD was more prevalent in winter than in other seasons. Underweight but not overweight was a risk factor for gestational VDD. Multivitamin use reduced risk of gestational VDD. Interestingly, 8.23% delivered preterm infants among subjects with VDD (adjusted RR: 4.02; 95% CI: 2.33, 6.92) and 3.81% among subjects with gestational vitamin D insufficiency (VDI) (adjusted RR: 2.07; 95% CI: 1.16, 3.71). Moreover, 2.59% delivered early preterm infants among subjects with VDD (adjusted RR: 2.97; 95% CI: 1.41, 6.24) and 0.49% among subjects with VDI (adjusted RR: 0.54; 95% CI: 0.19, 1.51). The incidence of late preterm delivery was 5.64% among subjects with VDD (adjusted RR: 3.90; 95% CI: 2.26, 6.72) and 3.32% among subjects with VDI (adjusted RR: 2.09; 95% CI: 1.17, 3.74). In conclusion, pre-pregnancy BMI, seasonality and multivitamin use are influent factors of gestational vitamin D status. Gestational VDD is associated with an increased risk of preterm delivery in Chinese population.