title: Interaction between smoking and body mass index and risk of oral clefts.
abstract: To examine maternal smoking and body mass index (BMI) interactions in contributing to risk of oral clefts.
  
  
  
  We studied 4935 cases and 10,557 controls from six population-based studies and estimated a pooled logistic regression of individual-level data, controlling for study fixed effects and individual-level risk factors.
  
  
  
  We found a significant negative smoking-BMI interaction, with cleft risk with smoking generally declining with higher BMI. For all clefts combined, the odds ratio for smoking was 1.61 (95% confidence interval [CI]: 1.39-1.86) at BMI 17 (underweight), 1.47 (95% CI: 1.34-1.62) at BMI 22 (normal weight), 1.35 (95% CI: 1.22-1.48) at BMI 27 (overweight), 1.21 (95% CI: 1.04-1.41) at BMI 33 (obese), and 1.13 (95% CI: 0.92-1.38) at BMI 37 (very obese). A negative interaction was also observed for isolated clefts and across cleft types but was more pronounced for cleft lip only and cleft palate only.
  
  
  
  Our findings suggest that the risk of oral clefts associated with maternal smoking is largest among underweight mothers, although the smoking-BMI interaction is strongest for cleft lip only and cleft palate only. BMI was not protective for the effects of smoking; a clinically relevant increase in smoking-related cleft risk was still present among heavier women.
authors.affiliation: Department of Health Management and Policy, University of Iowa, Iowa City; Department of Economics, University of Iowa, Iowa City; Department of Preventive & Community Dentistry, University of Iowa, Iowa City; Public Policy Center, University of Iowa, Iowa City. Electronic address: george-wehby@uiowa.edu.
authors.forename: George L
authors.initials: GL
authors.lastname: Wehby
authors.affiliation: Department of Orthodontics, College of Dentistry, University of Iowa, Iowa City.
authors.forename: Lina M Moreno
authors.initials: LM
authors.lastname: Uribe
authors.affiliation: National Institutes of Health, National Institute of Environmental Health Sciences, Epidemiology Branch, Durham, NC.
authors.forename: Allen J
authors.initials: AJ
authors.lastname: Wilcox
authors.affiliation: Department of Epidemiology, University of Southern Denmark, Odense, Denmark.
authors.forename: Kaare
authors.initials: K
authors.lastname: Christensen
authors.affiliation: Department of Epidemiology, College of Public Health, University of Iowa, Iowa City.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Romitti
authors.affiliation: Center for Epidemiologic Studies, Utah State University, Logan; Department of Nutrition, Dietetics, and Food Sciences, Utah State University, Logan.
authors.forename: Ronald G
authors.initials: RG
authors.lastname: Munger
authors.affiliation: Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway.
authors.forename: Rolv T
authors.initials: RT
authors.lastname: Lie
mesh_terms: D000293:Adolescent; D000328:Adult; D015992:Body Mass Index; D016022:Case-Control Studies; D002971:Cleft Lip / Q000453:epidemiology / Q000209:etiology*; D002972:Cleft Palate / Q000453:epidemiology / Q000209:etiology*; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D016015:Logistic Models; D009664:Norway / Q000453:epidemiology; D009765:Obesity / Q000150:complications*; D016017:Odds Ratio; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011297:Prenatal Exposure Delayed Effects; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D014481:United States / Q000453:epidemiology; D055815:Young Adult
keywords: Body mass index; Body weight; Cleft lip; Cleft palate; Obesity; Smoking