title: Low maternal vitamin D status during the second trimester of pregnancy: a cross-sectional study in Wuxi, China.
abstract: BACKGROUND
  Vitamin D deficiency is common in pregnant women, but an optimal serum vitamin D level during pregnancy has not been determined and remains an area of active research. Vitamin D data from large populations of pregnant Chinese women are still limited.
  
  
  OBJECTIVE
  To evaluate the vitamin D status of women in Eastern China during the second trimester of pregnancy.
  
  
  METHODS
  A hospital-based, cross-sectional, observational study. Serum 25-hydroxyvitamin D [25(OH)D] concentration was measured in samples from 5823 pregnant women in Wuxi City, China (latitude: 31.5o N), from January 2011 to June 2012.
  
  
  RESULTS
  The median serum 25(OH)D concentration was 34.0 nmol/L [2.5 nmol/L 25(OH)D = 1 ng/mL 25(OH)D]. Vitamin D deficiency [defined as 25(OH)D < 30 nmol/L according to the Institute of Medicine (National Academy of Sciences, Washington, D.C., USA)] or inadequacy [25(OH)D of 30-49.9 nmol/L] was identified in 40.7% and 38.0% of the women, respectively. Only 0.9% had a 25(OH)D level ≥ 80.0 nmol/L, which is the concentration recommended as adequate by the Endocrine Society (Washington, D.C., USA). Compared with older women, younger women were more likely to be deficient in vitamin D. There were significant differences in the 25(OH)D levels according to season. The 25(OH)D levels reached peak values in September and were correlated with (r = 0.337, P < 0.001), and fluctuated with, average monthly air temperatures.
  
  
  CONCLUSIONS
  There is a high prevalence of Vitamin D deficiency among pregnant Chinese women, and 25(OH)D levels varied according to season and air temperature. The results of this study also suggest that currently there is a big gap between the levels of Vitamin D detected in pregnant Chinese women and the levels recommended by the Endocrine Society.
authors: Department of Obstetrics, Wuxi Maternity and Child Health Hospital, Nanjing Medical University, Jiangsu, China; Perinatal Biology Center, Soochow University School of Medicine, Jiangsu, China.
authors: Jian-Ping
authors: JP
authors: Xiao
authors: Central Laboratory, Wuxi Maternity and Child Health Hospital, Nanjing Medical University, Jiangsu, China.
authors: Jia
authors: J
authors: Zang
authors: Department of Health Care, Wuxi Maternity and Child Health Hospital, Nanjing Medical University, Jiangsu, China.
authors: Jing-Jing
authors: JJ
authors: Pei
authors: Central Laboratory, Wuxi Maternity and Child Health Hospital, Nanjing Medical University, Jiangsu, China.
authors: Fei
authors: F
authors: Xu
authors: Department of Obstetrics, Wuxi Maternity and Child Health Hospital, Nanjing Medical University, Jiangsu, China.
authors: Yan
authors: Y
authors: Zhu
authors: Department of Newborn, Wuxi Maternity and Child Health Hospital, Nanjing Medical University, Jiangsu, China; Department of Obstetrics and Gynecology, Sherbrooke University Hospital Center, Sherbrooke, Canada.
authors: Xiang-Peng
authors: XP
authors: Liao
mesh_terms: D000293:Adolescent; D000328:Adult; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D011247:Pregnancy; D011248:Pregnancy Complications / Q000097:blood* / Q000453:epidemiology*; D011262:Pregnancy Trimester, Second / Q000097:blood*; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood* / Q000453:epidemiology*
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D