title: [Change trend of birth weight of twins in China, 1995-2012].
abstract: OBJECTIVE
  To understand the change trend of birth weight of twins in China from 1995 to 2012.
  
  
  METHODS
  A total of 10 827 twins born between 1995 and 2012 registered in national twin registry system in 8 provinces in China were included in this study. A retrospective study was conducted to analyze the change trend of twin's birth weight.
  
  
  RESULTS
  Mean birth weight of twins decreased by 0.01 kg every five years after adjusting sex, ovum type and place of birth (P = 0.041). The birth weight decreased both in superior twin and in inferior twin over time. After 2007, the birth weight of superior twin decreased by 0.008 kg each year, while the birth weight of inferior twin decreased by 0.014 kg each year. Mean relative difference in birth weight and birth weight discordant rate decreased before 2002, then increased from the lowest point 8.16% and 16.20% to highest point 9.99% and 22.40% respectively.
  
  
  CONCLUSIONS
  The birth weight of twins in China decreased between 1995 and 2012, while the birth weight discordant rate increased, suggesting that close attention should be paid to the discordance of twin body weight to reduce the risk of adverse health outcome.
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing 100191, China.
authors.forename: Qingqing
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing 100191, China. Email: canqing.yu@gmail.com.
authors.forename: Canqing
authors.initials: C
authors.lastname: Yu
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing 100191, China.
authors.forename: Wenjing
authors.initials: W
authors.lastname: Gao
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing 100191, China.
authors.forename: Weihua
authors.initials: W
authors.lastname: Cao
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing 100191, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Lyu
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing 100191, China.
authors.forename: Shengfeng
authors.initials: S
authors.lastname: Wang
authors.affiliation: Qingdao Center for Disease Control and Prevention.
authors.forename: Zengchang
authors.initials: Z
authors.lastname: Pang
authors.affiliation: Zhejiang Provincial Center for Disease Control and Prevention.
authors.forename: Liming
authors.initials: L
authors.lastname: Cong
authors.affiliation: Beijing Center for Disease Control and Prevention.
authors.forename: Zhong
authors.initials: Z
authors.lastname: Dong
authors.affiliation: Shanghai Center for Disease Control and Prevention.
authors.forename: Fan
authors.initials: F
authors.lastname: Wu
authors.affiliation: Jiangsu Provincial Center for Disease Control and Prevention.
authors.forename: Hua
authors.initials: H
authors.lastname: Wang
authors.affiliation: Sichuan Provincial Center for Disease Control and Prevention.
authors.forename: Xianping
authors.initials: X
authors.lastname: Wu
authors.affiliation: Tianjin Center for Disease Control and Prevention.
authors.forename: Dezheng
authors.initials: D
authors.lastname: Wang
authors.affiliation: School of Public Health, Harbin Medical University.
authors.forename: Binyou
authors.initials: B
authors.lastname: Wang
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing 100191, China. Email: lmlee@vip.163.com.
authors.forename: Liming
authors.initials: L
authors.lastname: Li
mesh_terms: D001723:Birth Rate; D001724:Birth Weight; D002681:China / Q000453:epidemiology; D006801:Humans; D007231:Infant, Newborn; D012042:Registries; D012189:Retrospective Studies; D014427:Twins