title: Long-term trends and seasonality of omphalocele during 1996-2010 in China: a retrospective analysis based on the hospital-based birth defects surveillance system.
abstract: BACKGROUND
  Little is known about secular trends and seasonal variation in the birth prevalence of omphalocele in China. This study aimed to explore the long-term trends and seasonality of this birth defect, to provide insight into the etiology and prevention of omphalocele.
  
  
  METHODS
  A retrospective analysis of all births with omphalocele (1322 cases in 8.8 million births) registered in the hospital-based Chinese Birth Defects Monitoring Network between January 1996 and September 2010. Negative binomial cyclical regression models were used to analyze the long-term trends and seasonal fluctuations of omphalocele occurrence in the southern and northern regions and urban and rural areas of China.
  
  
  RESULTS
  The total prevalence of omphalocele was 1.50 cases (95% confidence interval (CI): 1.42-1.58) per 10,000 births. There was no significant secular trend of omphalocele occurrence in China between 1996 and 2010. The observed prevalence of omphalocele in rural areas was 2.03-2.54 cases per 10,000 births between May and August, which was higher than that observed in other months. The highest prevalence of births with omphalocele in rural areas occurred at the end of June; on average, the prevalence of omphalocele at that time point increased by 20% (95% CI: 6-35%) compared with other months.
  
  
  CONCLUSIONS
  There were no long-term trends found for occurrence of omphalocele in China between 1996 and 2010; however, seasonality was observed for omphalocele in women living in rural areas. These results may help generate hypotheses for further study of environmental factors that vary by season.
authors.affiliation: Department of Epidemiology and Health Statistics, West China School of Public Health, Sichuan University, Sec.3 No.17, South RenMin Road, Chengdu, Sichuan, 610041, China. iiaoong@163.com.|National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sec.3 No.17, South RenMin Road, Chengdu, Sichuan, 610041, China. iiaoong@163.com.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Li
authors.affiliation: National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sec.3 No.17, South RenMin Road, Chengdu, Sichuan, 610041, China. daili_diamondlaser@126.com.
authors.forename: Li
authors.initials: L
authors.lastname: Dai
authors.affiliation: National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sec.3 No.17, South RenMin Road, Chengdu, Sichuan, 610041, China. wyxyanping@163.com.
authors.forename: Yanping
authors.initials: Y
authors.lastname: Wang
authors.affiliation: National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sec.3 No.17, South RenMin Road, Chengdu, Sichuan, 610041, China. yiling9@163.com.
authors.forename: Lin
authors.initials: L
authors.lastname: Yi
authors.affiliation: National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sec.3 No.17, South RenMin Road, Chengdu, Sichuan, 610041, China. dengchangfei@163.com.
authors.forename: Changfei
authors.initials: C
authors.lastname: Deng
authors.affiliation: National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sec.3 No.17, South RenMin Road, Chengdu, Sichuan, 610041, China. dengkui_1983@163.com.
authors.forename: Kui
authors.initials: K
authors.lastname: Deng
authors.affiliation: National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sec.3 No.17, South RenMin Road, Chengdu, Sichuan, 610041, China. 847829637@qq.com.
authors.forename: Guangxuan
authors.initials: G
authors.lastname: Zhou
authors.affiliation: National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sec.3 No.17, South RenMin Road, Chengdu, Sichuan, 610041, China. liqi210@126.com.
authors.forename: Qi
authors.initials: Q
authors.lastname: Li
authors.affiliation: National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sec.3 No.17, South RenMin Road, Chengdu, Sichuan, 610041, China. liuputer@163.com.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Liu
authors.affiliation: National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sec.3 No.17, South RenMin Road, Chengdu, Sichuan, 610041, China. dengying03@126.com.|Laboratory of Molecular Epidemiology for Birth Defects, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China. dengying03@126.com.
authors.forename: Ying
authors.initials: Y
authors.lastname: Deng
authors.affiliation: National Center for Birth Defect Monitoring, West China Second University Hospital, Sichuan University, Sec.3 No.17, South RenMin Road, Chengdu, Sichuan, 610041, China. zhujun028@163.com.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhu
authors.affiliation: Department of Epidemiology and Health Statistics, West China School of Public Health, Sichuan University, Sec.3 No.17, South RenMin Road, Chengdu, Sichuan, 610041, China. lixiaosong1101@126.com.
authors.forename: Xiaosong
authors.initials: X
authors.lastname: Li
mesh_terms: D002681:China / Q000453:epidemiology; D000013:Congenital Abnormalities / Q000453:epidemiology; D062665:Epidemiological Monitoring; D006554:Hernia, Umbilical / Q000453:epidemiology* / Q000209:etiology; D006801:Humans; D007231:Infant, Newborn; D015995:Prevalence; D012189:Retrospective Studies; D012307:Risk Factors; D012424:Rural Population / Q000706:statistics & numerical data; D012621:Seasons