title: History of oral contraceptive use and risk of spontaneous abortion.
abstract: OBJECTIVE
  To examine the association between pregravid oral contraceptive (OC) use and spontaneous abortion (SAB).
  
  
  METHODS
  In an Internet-based preconception cohort study of 4862 Danish pregnancy planners, we used Cox proportional hazards models to estimate adjusted hazard ratios and 95% confidence intervals (CIs) for the association between OC use and SAB. We controlled for maternal age, physical activity, parity, education, alcohol and caffeine consumption, body mass index, and smoking.
  
  
  RESULTS
  Compared with women who discontinued OCs >1 year before conception, HRs were 0.95 (95% confidence interval (CI) = 0.77-1.17), 0.99 (95% CI = 0.82-1.19), and 0.80 (95% CI = 0.60-1.06) for women who discontinued OCs 7-12, 2-6, and 0-1 months before conception, respectively. Compared with less than 4 years of OC use, HRs for 4-7, 8-11, and 12 years or more of OC use were 1.05 (95% CI = 0.80-1.37), 0.92 (95% CI = 0.71-1.19), and 0.88 (95% CI = 0.65-1.19), respectively. Dose of estrogen and generation of progestin were not materially associated with SAB risk.
  
  
  CONCLUSIONS
  We found no evidence that pregravid OC use is associated with an increase in SAB. Use within 1 month of conception was associated with a slightly lower risk of SAB, but this may be due to increased reproductive fitness in women who conceive quickly after discontinuation of OCs.
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, MA. Electronic address: kahahn@bu.edu.
authors.forename: Kristen A
authors.initials: KA
authors.lastname: Hahn
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, MA.
authors.forename: Elizabeth E
authors.initials: EE
authors.lastname: Hatch
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, MA; RTI Health Solutions, Research Triangle Park, NC.
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Rothman
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus N, Denmark.
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Mikkelsen
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, MA.
authors.forename: Susan B
authors.initials: SB
authors.lastname: Brogly
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, MA; Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus N, Denmark.
authors.forename: Henrik T
authors.initials: HT
authors.lastname: Sørensen
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus N, Denmark.
authors.forename: Anders H
authors.initials: AH
authors.lastname: Riis
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, MA; Slone Epidemiology Center, Boston University, Boston, MA.
authors.forename: Lauren A
authors.initials: LA
authors.lastname: Wise
mesh_terms: D000022:Abortion, Spontaneous / Q000209:etiology*; D000328:Adult; D015331:Cohort Studies; D003276:Contraceptives, Oral / Q000009:adverse effects*; D003718:Denmark; D005260:Female; D006801:Humans; D008423:Maternal Age; D008875:Middle Aged; D011247:Pregnancy; D016016:Proportional Hazards Models; D012307:Risk Factors; D012959:Socioeconomic Factors; D013997:Time Factors; D055815:Young Adult
chemical_list: D003276:Contraceptives, Oral
keywords: Cohort study; Oral contraceptive; Spontaneous abortion