title: Body mass index, physical activity and fecundability in a North American preconception cohort study.
abstract: To evaluate the association between adiposity, physical activity (PA), and fecundability.
  
  
  
  Prospective cohort study.
  
  
  
  Not applicable.
  
  
  
  A total of 2,062 female pregnancy planners from the United States and Canada who were enrolled during the preconception period.
  
  
  
  None.
  
  
  
  Self-reported pregnancy. Fecundability ratios (FRs) and 95% confidence intervals (CIs) were estimated using proportional probabilities models that adjusted for potential confounders.
  
  
  
  Relative to body mass index (BMI) 18.5-24 kg/m(2), FRs for BMI <18.5, 25-29, 30-34, 35-39, 40-44, and ≥45 kg/m(2) were 1.05 (95% CI 0.76-1.46), 1.01 (95% CI 0.89-1.15), 0.98 (95% CI 0.82-1.18), 0.78 (95% CI 0.60-1.02), 0.61 (95% CI 0.42-0.88), and 0.42 (95% CI 0.23-0.76), respectively. Reduced fecundability was observed among women with the largest waist-to-hip ratios (≥0.85 vs. <0.75; FR = 0.87, 95% CI 0.74-1.01) and waist circumferences (≥36 vs. <26 inches [≥90 vs. <66 cm]; FR = 0.80, 95% CI 0.59-1.01). Tendency to gain weight in the chest/shoulders (FR = 0.63, 95% CI 0.36-1.08) and waist/stomach (FR = 0.90, 95% CI 0.79-1.02), relative to hips/thighs, was associated with lower fecundability. Moderate PA was associated with increased fecundability (≥5 vs. <1 h/wk; FR = 1.26, 95% CI 0.96-1.65), but there was no dose-response relation. Among overweight/obese women (BMI ≥25 kg/m(2)), fecundability was 27% higher for vigorous PA of ≥5 versus <1 h/wk (95% CI 1.02-1.57).
  
  
  
  Various measures of overall and central adiposity were associated with decreased fertility among pregnancy planners. Vigorous PA was associated with improved fertility among overweight and obese women only; moderate PA was associated with improved fertility among all women.
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts. Electronic address: craigm@bu.edu.
authors.forename: Craig J
authors.initials: CJ
authors.lastname: McKinnon
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts.
authors.forename: Elizabeth E
authors.initials: EE
authors.lastname: Hatch
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts; RTI Health Solutions, Research Triangle Park, North Carolina.
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Rothman
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Mikkelsen
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts.
authors.forename: Amelia K
authors.initials: AK
authors.lastname: Wesselink
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts.
authors.forename: Kristen A
authors.initials: KA
authors.lastname: Hahn
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts; Slone Epidemiology Center, Boston University School of Public Health, Boston, Massachusetts.
authors.forename: Lauren A
authors.initials: LA
authors.lastname: Wise
mesh_terms: D050154:Adiposity; D000328:Adult; D015992:Body Mass Index; D002170:Canada; D015444:Exercise; D005260:Female; D005298:Fertility; D006304:Health Status; D006801:Humans; D007247:Infertility, Female / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D009765:Obesity / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology; D011247:Pregnancy; D011446:Prospective Studies; D060728:Reproductive Health; D012307:Risk Factors; D057566:Self Report; D061685:Time-to-Pregnancy; D014481:United States; D016387:Women's Health; D055815:Young Adult
keywords: Fecundability; obesity; physical activity; preconception cohort; time-to-pregnancy