title: Reproductive characteristics and risk of uterine leiomyomata.
abstract: OBJECTIVE
  To evaluate whether menstrual and reproductive characteristics may influence development of uterine leiomyomata since sex steroid hormones have been hypothesized to play a role in their development.
  
  
  METHODS
  A prospective cohort study (Nurses' Health Study II).
  
  
  METHODS
  Participants were identified from 14 states and followed for 14 years.
  
  
  METHODS
  A cohort of 116,609 female registered nurses ages 25-42 at baseline.
  
  
  METHODS
  We obtained data on uterine leiomyomata incidence and exposures through biennial questionnaires. We calculated hazard ratios and 95% confidence intervals adjusted for known and suspected risk factors.
  
  
  METHODS
  Uterine leiomyomata confirmed by ultrasound or hysterectomy.
  
  
  RESULTS
  During 1,163,439 person-years of follow-up, 9,847 self-reported cases of hysterectomy- or ultrasound-confirmed uterine leiomyomata were reported. We observed a lower incidence of uterine leiomyomata with later age at menarche, longer menstrual cycles, parity, later age at first and last birth, shorter time since last birth, and breastfeeding.
  
  
  CONCLUSIONS
  Hormonal and anatomical changes associated with menstruation and pregnancy may influence uterine leiomyomata incidence.
authors.affiliation: Department of Obstetrics and Gynecology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA. kterry@partners.org
authors.forename: Kathryn L
authors.initials: KL
authors.lastname: Terry
authors.forename: Immaculata
authors.initials: I
authors.lastname: De Vivo
authors.forename: Susan E
authors.initials: SE
authors.lastname: Hankinson
authors.forename: Stacey A
authors.initials: SA
authors.lastname: Missmer
mesh_terms: D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D005260:Female; D005298:Fertility / Q000502:physiology; D005500:Follow-Up Studies; D006801:Humans; D007889:Leiomyoma / Q000453:epidemiology / Q000209:etiology*; D008597:Menstrual Cycle; D009726:Nurses; D011247:Pregnancy; D012098:Reproduction / Q000502:physiology*; D012307:Risk Factors; D014594:Uterine Neoplasms / Q000453:epidemiology / Q000209:etiology*; D055815:Young Adult