Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 47 8 2018 08 01 1145 1150 Ling YANG Dept. of Obstetrics, Changning Maternity and Infant Health Hospital, Shanghai, China Lige SONG Dept. of Endocrinology, Tongji Hospital, School of Medicine, Tongji University, Shanghai, China Xiao XU Dept. of Endocrinology, Tongji Hospital, School of Medicine, Tongji University, Shanghai, China Yihan LIU Dept. of Endocrinology, Tongji Hospital, School of Medicine, Tongji University, Shanghai, China Huijuan LI Dept. of Endocrinology, Tongji Hospital, School of Medicine, Tongji University, Shanghai, China LongYing TANG Dept. of Obstetrics, Changning Maternity and Infant Health Hospital, Shanghai, China 2018 08 01 2018 08 01 Background: Vitamin D plays important roles in various physiological processes. Vitamin D deficiency is common among pregnant women in some regions, such as China. Our study aimed to determine the prevalence of Vitamin D deficiency during second trimester of pregnancy in Shanghai China, and explore its risk factors and effects on pregnant outcomes. Methods: Overall, 23100 pregnant women (2013 to 2017, Shanghai, China) were included and vitamin D concentrations were measured at 16 weeks of gestation. Correlations between vitamin D concentrations and participants’ general data and maternal and infant outcomes were analyzed by chi square test. Non-conditional multivariate logistic regression analysis was used to screen the independent risk factors for vitamin D deficiency. Results: Vitamin D deficiency was significantly correlated with aging, education level, smoking, dirking, BMI before pregnancy, body weight gain during pregnancy (P<0.01), the use of vitamin D supplement and milk consumption, and older than 30 years, drinking, smoking, BMI before pregnancy> 36, body weight gain during pregnancy< 40g per day, no daily milk consumption, no vitamin D supplement, and education lever below college were independent risk factors for vitamin D deficiency in second trimester of pregnancy. In addition, vitamin D deficiency in second trimester of pregnancy was closely correlated with the occurrence of a serious of adverse maternal and infant outcomes. Conclusion: Vitamin D deficiency was still common among women in second trimester of pregnancy in Shanghai China. Vitamin D deficiency was closely correlated with the occurrence of a serious of adverse maternal and infant outcomes.   https://ijph.tums.ac.ir/index.php/ijph/article/view/14292 https://ijph.tums.ac.ir/index.php/ijph/article/download/14292/6082