title: Caffeinated beverage and soda consumption and time to pregnancy.
abstract: BACKGROUND
  Many epidemiologic studies have evaluated the association between caffeine and fertility, with inconsistent results. Some studies suggest that various caffeine-containing beverages may affect fertility differently.
  
  
  METHODS
  We evaluated the relation of caffeine, coffee, tea, and sodas with time to pregnancy in a prospective cohort study of 3628 women planning a pregnancy, in Denmark (2007-2010). Women reported beverage intake at baseline and every 8 weeks during follow-up until they became pregnant or for up to 12 cycles. We used discrete-time Cox proportional hazards regression to estimate fecundability ratios (FRs) and 95% confidence intervals (CIs), controlling for potential confounders.
  
  
  RESULTS
  There was little relation between fecundability and caffeine intake of 300+ mg/day compared with < 100 mg/day (FR = 1.04 [95% CI = 0.90-1.21]) or coffee intake of 3+ servings/day compared with none (1.05 [0.85-1.33]). Soda consumption was associated with reduced fecundability: for all types of sodas combined, the adjusted FRs were 0.89 (0.80-0.98), 0.85 (0.71-1.02), 0.84 (0.57-1.25), and 0.48 (0.21-1.13) for < 1, 1, 2, and 3+ servings per day, respectively, compared with none. Tea drinking was associated with a slight increase in fecundability, with FR = 1.27 (0.98-1.64) for 2+ servings/day versus none.
  
  
  CONCLUSIONS
  In this prospective study of time to pregnancy, the association between caffeine intake and fertility differed by beverage type. Although we controlled for many confounders, our findings of reduced fecundability among soda drinkers and increased fecundability among tea drinkers could have resulted from confounding by unmeasured lifestyle characteristics.
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, MA, USA. eehatch@bu.edu
authors.forename: Elizabeth E
authors.initials: EE
authors.lastname: Hatch
authors.forename: Lauren A
authors.initials: LA
authors.lastname: Wise
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Mikkelsen
authors.forename: Tina
authors.initials: T
authors.lastname: Christensen
authors.forename: Anders H
authors.initials: AH
authors.lastname: Riis
authors.forename: Henrik Toft
authors.initials: HT
authors.lastname: Sørensen
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Rothman
mesh_terms: D000293:Adolescent; D000328:Adult; D001628:Beverages / Q000009:adverse effects*; D002110:Caffeine / Q000009:adverse effects*; D002253:Carbonated Beverages / Q000009:adverse effects; D000697:Central Nervous System Stimulants / Q000009:adverse effects*; D003069:Coffee / Q000009:adverse effects; D004034:Diet Surveys; D005260:Female; D005298:Fertility / Q000187:drug effects*; D005500:Follow-Up Studies; D006801:Humans; D011247:Pregnancy / Q000187:drug effects*; D016016:Proportional Hazards Models; D011446:Prospective Studies; D011795:Surveys and Questionnaires; D013662:Tea / Q000009:adverse effects; D013997:Time Factors; D055815:Young Adult
chemical_list: D000697:Central Nervous System Stimulants; D003069:Coffee; D013662:Tea; D002110:Caffeine