title: Pregnancy history and risk of endometrial cancer.
abstract: BACKGROUND
  Epidemiologic studies are consistent in finding that women who have had at least one birth are less likely to develop endometrial cancer. Less clear is whether timing of pregnancies during reproductive life influences risk, and the degree to which incomplete pregnancies are associated with a reduced risk.
  
  
  METHODS
  We evaluated pregnancy history in relation to endometrial cancer risk using data from a series of 4 population-based endometrial cancer case-control studies of women 45-74 years of age (1712 cases and 2134 controls) during 1985-2005 in western Washington State. Pregnancy history and information on other potential risk factors were collected by in-person interviews.
  
  
  RESULTS
  Older age at first birth was associated with a reduced risk of endometrial cancer after adjustment for number of births and age at last birth (test for trend P = 0.004). The odds ratio comparing women at least 35 years of age at their first birth with those younger than 20 years was 0.34 (95% confidence interval = 0.14-0.84). Age at last birth was not associated with risk after adjustment for number of births and age at first birth (test for trend P = 0.830). Overall, a history of incomplete pregnancies was not associated with endometrial cancer risk to any appreciable degree.
  
  
  CONCLUSIONS
  In this study, older age at first birth was more strongly associated with endometrial cancer risk than was older age at last birth. To date, there remains some uncertainty in the literature on this issue.
authors.affiliation: Department of Epidemiology, School of Public Health, University of Washington, Seattle, WA 98195, USA. gpocobel@u.washington.edu
authors.forename: Gaia
authors.initials: G
authors.lastname: Pocobelli
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Doherty
authors.forename: Lynda F
authors.initials: LF
authors.lastname: Voigt
authors.forename: Shirley A
authors.initials: SA
authors.lastname: Beresford
authors.forename: Deirdre A
authors.initials: DA
authors.lastname: Hill
authors.forename: Chu
authors.initials: C
authors.lastname: Chen
authors.forename: Mary Anne
authors.initials: MA
authors.lastname: Rossing
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Holmes
authors.forename: Zorawar S
authors.initials: ZS
authors.lastname: Noor
authors.forename: Noel S
authors.initials: NS
authors.lastname: Weiss
mesh_terms: D000230:Adenocarcinoma / Q000453:epidemiology*; D000367:Age Factors; D000368:Aged; D016022:Case-Control Studies; D016889:Endometrial Neoplasms / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D016017:Odds Ratio; D010298:Parity; D011159:Population Surveillance; D011247:Pregnancy; D012042:Registries; D017584:Reproductive History; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014861:Washington / Q000453:epidemiology