title: Proportion of neural tube defects attributable to known risk factors.
abstract: BACKGROUND
  Recognized risk factors for neural tube defects (NTDs) poorly predict population-level NTD risk. However, the proportion of NTDs that can be attributed to these risk factors is uncertain.
  
  
  METHODS
  To determine the proportion of NTD cases that is attributable to known or suspected risk factors (i.e., female infant sex, family history of NTDs, and maternal Hispanic ethnicity, obesity, pregestational diabetes, gestational diabetes, low dietary folate intake, lack of folic acid supplementation, anticonvulsant use, and hot tub or sauna use), we estimated the adjusted population attributable fraction (aAF) for each factor, using the method of Eide and Geffler and data from the National Birth Defects Prevention Study.
  
  
  RESULTS
  Our analyses of these data indicate that the proportion of cases of spina bifida and anencephaly that can be attributed to known risk factors is 28% and 44%, respectively. For spina bifida, the factor with the greatest attributable fraction was maternal obesity (aAF, 10%), whereas for anencephaly it was Hispanic ethnicity (aAF, 15%).
  
  
  CONCLUSIONS
  Our analyses indicate that known risk factors account for <50% of NTD cases. Hence, the majority of NTD cases are attributable to, as yet, unidentified factors. These findings highlight the need for continued research to identify genetic and additional nongenetic risk factors for NTDs. Further, these findings suggest that strategies that aim to reduce the risk of NTDs associated with maternal Hispanic ethnicity and obesity may have the greatest impact on the population prevalence of these conditions.
authors: Human Genetics Center, Division of Epidemiology, Human Genetics and Environmental Sciences, University of Texas School of Public Health, Houston, TX 77030, USA.
authors: A J
authors: AJ
authors: Agopian
authors: Sarah C
authors: SC
authors: Tinker
authors: Philip J
authors: PJ
authors: Lupo
authors: Mark A
authors: MA
authors: Canfield
authors: Laura E
authors: LE
authors: Mitchell
mesh_terms: D000328:Adult; D000757:Anencephaly / Q000453:epidemiology* / Q000209:etiology; D015984:Causality; D016208:Databases, Factual; D005260:Female; D006630:Hispanic or Latino / Q000208:ethnology; D006801:Humans; D008297:Male; D018811:Maternal Exposure; D009035:Mothers; D009765:Obesity / Q000150:complications / Q000453:epidemiology; D011247:Pregnancy; D011248:Pregnancy Complications; D018570:Risk Assessment; D012307:Risk Factors; D016135:Spinal Dysraphism / Q000453:epidemiology* / Q000209:etiology; D014481:United States / Q000453:epidemiology