title: Maternal body mass index and the association between folic acid supplements and neural tube defects.
abstract: OBJECTIVE
  To study the influence of maternal body mass index (BMI) on the association between folic acid supplementation and neural tube defects (NTDs) risk in offspring.
  
  
  METHODS
  A hospital-based, case-control study was conducted between 2006 and 2008 on 459 mothers with NTDs-affected births and 459 mothers without NTDs-affected births. Logistic regression models examined the associations between folic acid supplementation and the NTDs risk in offspring for all mothers, underweight/normal weight mothers (BMI<24.0) and overweight/obese mothers (BMI ≥24.0). The effects were evaluated by adjusted odds ratio (AOR) and 95% confidence intervals (CIs) with SAS 9.1.3 software.
  
  
  RESULTS
  The overall AOR for periconceptional folic acid supplementation was 0.315 (95% CI = 0.172-0.577) when compared with no supplements. Stratified by maternal BMI, the AOR for periconceptional folic acid supplementation in overweight/obese mothers was greater than in underweight/normal weight mothers (0.646 vs. 0.208). The AOR for folic acid supplementation within 3 months before conception was 0.711 (95% CI = 0.323-1.563) in all mothers. Stratified by maternal BMI, the AOR for folic acid supplementation within 3 months before conception in overweight/obese mothers was greater than in underweight/normal weight mothers (0.658 vs. 0.527).
  
  
  CONCLUSIONS
  The association between folic acid supplementation and the reduced NTDs risk was weaker in overweight/obese mothers (BMI ≥24.0) than in underweight/normal weight mothers (BMI <24.0).
authors.affiliation: Department of Epidemiology and Health Statistics, School of Public Health, Shandong University, Jinan, China.
authors.forename: Meng
authors.initials: M
authors.lastname: Wang
authors.forename: Zhi-Ping
authors.initials: ZP
authors.lastname: Wang
authors.forename: Li-Jie
authors.initials: LJ
authors.lastname: Gao
authors.forename: Rui
authors.initials: R
authors.lastname: Gong
authors.forename: Xi-Hong
authors.initials: XH
authors.lastname: Sun
authors.forename: Zhong-Tang
authors.initials: ZT
authors.lastname: Zhao
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D015992:Body Mass Index; D016001:Confidence Intervals; D003430:Cross-Sectional Studies; D019587:Dietary Supplements; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage*; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D016015:Logistic Models; D008297:Male; D008429:Maternal Welfare; D009436:Neural Tube Defects / Q000453:epidemiology / Q000517:prevention & control*; D009765:Obesity / Q000453:epidemiology*; D016017:Odds Ratio; D011247:Pregnancy; D011295:Prenatal Care / Q000379:methods; D011379:Prognosis; D012016:Reference Values; D018570:Risk Assessment; D055815:Young Adult
chemical_list: D005492:Folic Acid
keywords: Body mass index; Folic acid; Neural tube defects