title: Tubal sterilization and subsequent ectopic pregnancy. A case-control study.
abstract: OBJECTIVE
  To assess the relative risk of ectopic pregnancy associated with postpartum or interval tubal sterilization.
  
  
  METHODS
  Case-control study using a comparison group of women of reproductive age at risk of pregnancy.
  
  
  METHODS
  Group Health Cooperative of Puget Sound, a health maintenance organization based in Seattle, Wash. organization based in Seattle, Wash.
  
  
  METHODS
  Cases were 249 enrollees diagnosed as having an ectopic pregnancy between October 1, 1981, and September 30, 1986. Controls were 835 randomly selected enrollees matched to cases on age and county of residence.
  
  
  METHODS
  Information on interval sterilization history was obtained from interviews, examination of medical records, automated hospitalization files and a previously validated algorithm. A logistic regression model was used to estimate relative risks (RRs) for sterilized women compared with women using other types of or no contraception at the reference date.
  
  
  RESULTS
  Controlling for age, county, race, smoking, income, gravidity, and prior use of a Dalkon Shield intrauterine device, the risk of ectopic pregnancy in women who had undergone interval sterilization was 3.7 (95% confidence interval [CI], 1.7 to 8.0) times that of women currently using oral contraception and 2.8 (95% CI, 1.5 to 5.5) times that of women currently using barrier contraceptive methods. Use of interval sterilization was associated with a risk of ectopic pregnancy similar to that of women using intrauterine devices (RR, 0.8; 95% CI, 0.4 to 1.7) and a risk lower than that of women who were not using contraception (RR, 0.2; 95% CI, 0.1 to 0.3). The corresponding RRs associated with postpartum sterilization were lower: 1.2 (95% CI, 0.3 to 3.9), 0.9 (95% CI, 0.3 to 2.8), 0.3 (95% CI, 0.1 to 0.8), and 0.1 (95% CI, 0.0 to 0.2), respectively.
  
  
  CONCLUSIONS
  Tubal sterilization provides some protection against extrauterine as well as intrauterine pregnancy. It is likely that postpartum sterilization can be a safe alternative to all types of temporary contraception in terms of risk of ectopic pregnancy, while some types of interval sterilization may lead to an increased risk, in comparison with use of oral contraceptives or barrier methods.
authors.affiliation: Department of Epidemiology, School of Public Health and Community Medicine, University of Washington, Seattle 98195.
authors.forename: V L
authors.initials: VL
authors.lastname: Holt
authors.forename: J
authors.initials: J
authors.lastname: Chu
authors.forename: J R
authors.initials: JR
authors.lastname: Daling
authors.forename: A S
authors.initials: AS
authors.lastname: Stergachis
authors.forename: N S
authors.initials: NS
authors.lastname: Weiss
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D003267:Contraception / Q000379:methods; D005260:Female; D006801:Humans; D016015:Logistic Models; D049590:Postpartum Period; D011247:Pregnancy; D011271:Pregnancy, Ectopic / Q000453:epidemiology / Q000209:etiology*; D012044:Regression Analysis; D012307:Risk Factors; D013246:Sterilization, Tubal; D014861:Washington / Q000453:epidemiology