title: Effects of folic acid supplementation during different pregnancy periods and relationship with the other primary prevention measures to neural tube defects.
abstract: OBJECTIVE
  To find out the prevention effects of folic acid supplements during different pregnancy periods on neural tube defects (NTDs) and the relationship of folic acid supplements with the other NTDs' primary preventive measures.
  
  
  METHODS
  A 1:1 case-control study was conducted. Four hundred and fifty-nine women who delivered or gestate infants/fetuses with NTDs in the last two years were randomly selected as cases and were matched with women who delivered babies without obvious birth defects as controls.
  
  
  RESULTS
  For anencephaly, folic acid supplementation during the periconceptional period and preconceptional period has a 57-83% reduction in risk of NTDs(ORs ranged from 0.17 to 0.43). For spina bifida, folic acid supplementation during the periconceptional period has a 79% reduction in risk of NTDs (OR = 0.21). For encephalocele, folic acid supplementation during the periconceptional period has a 67% reduction in risk of NTDs (OR = 0.33). The prevention effects on NTDs were significant when these preventive measures combined with folic acid supplements during the periconceptional period, with OR 0.04, 0.07, 0.10 and 0.11.
  
  
  CONCLUSIONS
  The specific effects of folic acid supplementation during different periods show the reduction in the risk of NTDs, anencephaly, spina bifida, encephalocele. During periconceptional period, folic acid supplements have preventive effects on all NTDs' subtypes.
authors.affiliation: a Institute of Population Research, Peking University , Beijing , China .|b Department of Epidemiology and Health Statistics , School of Public Health, Shandong University , Jinan , China .|c China Rehabilitation Research Centre for Deaf Children , Beijing , China .
authors.forename: Rui
authors.initials: R
authors.lastname: Gong
authors.affiliation: b Department of Epidemiology and Health Statistics , School of Public Health, Shandong University , Jinan , China .
authors.forename: Zhi-Ping
authors.initials: ZP
authors.lastname: Wang
authors.affiliation: d Zhejiang Provincial Center for Disease Control and Prevention , Hangzhou City , China.
authors.forename: Meng
authors.initials: M
authors.lastname: Wang
authors.affiliation: b Department of Epidemiology and Health Statistics , School of Public Health, Shandong University , Jinan , China .
authors.forename: Li-Jie
authors.initials: LJ
authors.lastname: Gao
authors.affiliation: b Department of Epidemiology and Health Statistics , School of Public Health, Shandong University , Jinan , China .
authors.forename: Zhong-Tang
authors.initials: ZT
authors.lastname: Zhao
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D019587:Dietary Supplements; D005260:Female; D005492:Folic Acid / Q000627:therapeutic use*; D006801:Humans; D008875:Middle Aged; D009436:Neural Tube Defects / Q000517:prevention & control*; D011247:Pregnancy; D011322:Primary Prevention / Q000379:methods*; D012044:Regression Analysis; D011795:Surveys and Questionnaires; D014803:Vitamin B Complex / Q000627:therapeutic use*; D055815:Young Adult
chemical_list: D014803:Vitamin B Complex; D005492:Folic Acid
keywords: Anencephaly; folic acid; neural tube defects; periconceptional period; preventive measures; spina bifida