METHODS: A total of 34,417 pregnant women in Shanghai were included in this study from January 2014 to December 2017, and the serum
25-hydroxyvitamin D [25(
OH)D] concentrations were measured at 16th week of gestation by electrochemiluminescence assay. Seventy five grams of
glucose was used to conduct oral
glucose tolerance test during 24-28th week of gestational in all enrolled persons and the
birth weight of newborns was recorded.
RESULTS: The median serum 25(
OH) D concentration in the pregnant women during 4 years was 42.87 nmol/L (32.88-51.90 nmol/L). 9.9% of the population were severe
vitamin D deficient [25(
OH)D < 25 nmol/L], 60.1% were deficient [25 nmol/L ≤ 25(
OH)D < 50 nmol/L], 28.4% were insufficient [50 nmol/L ≤ 25(
OH)D < 75 nmol/L] and only 1.6% of the enrolled population reached the level of adequate [25(
OH)D ≥ 75 nmol/L]. Serum 25(
OH) D concentrations showed significant difference among seasons with the highest level in winter and the lowest level in summer. Women with advanced maternal age were more likely to have better
vitamin D status compared with younger women. The 25(
OH) D levels were significantly different among 2014-2017. The year of 2017 had the highest 25(
OH) D level with the median serum concentration reaching 47.80 nmol/L (41.00-55.00 nmol/L), while the lowest appeared in 2016 which has median 25(
OH) D concentration at 38.87 nmol/L (28.76-49.97 nmol/L). No relations were found between the 25(
OH) D status and the rate of
gestational diabetes or low birth weight of newborns.
CONCLUSION: Pregnant women in Shanghai were generally deficient in
vitamin D status and the level of
vitamin D was related to season and age. No evidence showed
vitamin D deficiency in pregnant women contributes to the rate of
gestational diabetes or low birth weight of newborns in this study. These results suggest that most of the pregnant women may need
vitamin D supplementation to achieve adequate
vitamin D level.