title: Maternal urinary manganese and risk of low birth weight: a case-control study.
abstract: BACKGROUND
  Manganese (Mn) is an essential element for humans, but exposure to high levels has been associated with adverse developmental outcomes. Early epidemiological studies evaluating the effect of Mn on fetal growth are inconsistent.
  
  
  METHODS
  We investigated the association between maternal urinary Mn during pregnancy and the risk of low birth weight (LBW). Mn concentrations in maternal urine samples collected before delivery were measured in 816 subjects (204 LBW cases and 612 matched controls) recruited between 2012 and 2014 in Hubei Province, China.
  
  
  RESULTS
  The median Mn concentration in maternal urine was 0.69 μg/g creatinine. Compared to the medium tertile of Mn levels, an increased risk of LBW was observed for the lowest tertile (≤0.30 μg/g creatinine) [adjusted odds ratio (OR) = 1.28; 95 % confidence interval (CI) = 0.67, 2.45], and a significantly increased risk of LBW was observed for the highest tertile (≥1.16 μg/g creatinine) [adjusted OR = 2.04; 95 % CI = 1.12, 3.72]. A curvilinear relationship between maternal urinary Mn and risk of LBW was observed, showing that the concentration at 0.43 μg/g creatinine was the point of inflection. Similar associations were observed among the mothers with female infants and among the younger mothers < 28 years old. However, among the mothers with male infants or the older mothers ≥ 28 years old, only higher levels of Mn were positively associated with LBW.
  
  
  CONCLUSIONS
  Lower or higher levels of maternal urinary Mn are associated with LBW, though only the association of LBW risk and higher levels of Mn was statistically significant. The findings also show that the associations may vary by maternal age and infant sex, but require confirmation in other populations.
authors: Key Laboratory of Environment and Health (HUST), Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health (Incubation), school of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China. xiawei@hust.edu.cn.
authors: Wei
authors: W
authors: Xia
authors: Key Laboratory of Environment and Health (HUST), Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health (Incubation), school of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China.
authors: Yanqiu
authors: Y
authors: Zhou
authors: Department of Environmental Health Sciences, Brown School of Public Health, Providence, RI, USA.
authors: Tongzhang
authors: T
authors: Zheng
authors: Women and Children Medical and Healthcare Center of Wuhan, Wuhan, Hubei, People's Republic of China.
authors: Bin
authors: B
authors: Zhang
authors: Department of Environmental Health Sciences, Yale School of Public Health, New Haven, CT, USA.
authors: Bryan A
authors: BA
authors: Bassig
authors: Key Laboratory of Environment and Health (HUST), Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health (Incubation), school of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China.
authors: Yuanyuan
authors: Y
authors: Li
authors: Wise Laboratory of Environmental and Genetic Toxicology, Portland, ME, USA.
authors: John Pierce
authors: JP
authors: Wise
authors: Women and Children Medical and Healthcare Center of Wuhan, Wuhan, Hubei, People's Republic of China.
authors: Aifen
authors: A
authors: Zhou
authors: Key Laboratory of Environment and Health (HUST), Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health (Incubation), school of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China.
authors: Yanjian
authors: Y
authors: Wan
authors: Key Laboratory of Environment and Health (HUST), Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health (Incubation), school of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China.
authors: Youjie
authors: Y
authors: Wang
authors: Key Laboratory of Environment and Health (HUST), Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health (Incubation), school of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China.|Women and Children Medical and Healthcare Center of Wuhan, Wuhan, Hubei, People's Republic of China.
authors: Chao
authors: C
authors: Xiong
authors: Women and Children Medical and Healthcare Center of Wuhan, Wuhan, Hubei, People's Republic of China.
authors: Jinzhu
authors: J
authors: Zhao
authors: Macheng Maternal and Child Health Care Hospital, Macheng, Hubei, People's Republic of China.
authors: Zhengkuan
authors: Z
authors: Li
authors: Ezhou Maternal and Child Health Hospital, Ezhou, Hubei, People's Republic of China.
authors: Yuanxiang
authors: Y
authors: Yao
authors: Key Laboratory of Environment and Health (HUST), Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health (Incubation), school of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China.
authors: Jie
authors: J
authors: Hu
authors: Key Laboratory of Environment and Health (HUST), Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health (Incubation), school of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China.
authors: Xinyun
authors: X
authors: Pan
authors: Key Laboratory of Environment and Health (HUST), Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health (Incubation), school of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China. xust@hust.edu.cn.
authors: Shunqing
authors: S
authors: Xu
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002681:China; D005260:Female; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D008297:Male; D008345:Manganese / Q000652:urine*; D008423:Maternal Age; D016017:Odds Ratio; D011247:Pregnancy; D012306:Risk
chemical_list: D008345:Manganese