title: Epidemiology of endometriosis in women attending family planning clinics.
abstract: OBJECTIVE
  To describe the epidemiology of endometriosis in women attending family planning clinics with special reference to contraceptive methods.
  
  
  METHODS
  Non-randomised cohort study with follow up of subjects for up to 23 years. Disease was measured by first hospital admission rates since endometriosis can be diagnosed with accuracy only at laparotomy or laparoscopy.
  
  
  METHODS
  17 family planning centres in England and Scotland.
  
  
  METHODS
  17,032 married white women aged 25-39 years at entry during 1968-74 who were taking oral contraceptives or using an intrauterine device or diaphragm. About 99% of the women approached agreed to participate and annual loss to follow up was about 0.3%.
  
  
  METHODS
  Diagnosis of endometriosis, age, parity, and history of contraceptive use.
  
  
  RESULTS
  Endometriosis was significantly related to age, peaking at ages 40-44 (chi 2 for heterogeneity = 30.9, p < 0.001). Endometriosis was not linked to duration of taking oral contraceptives. Nevertheless, the risk of endometriosis was low in women currently taking oral contraceptives (relative risk 0.4; 95% confidence interval 0.2 to 0.7), but higher in women who had formerly taken them (1.8; 1.0 to 3.1 in women who had stopped 25-48 months previously) compared with women who had never taken the pill. A similar pattern was seen for use of intrauterine devices (relative risk 0.4 (0.2 to 0.7) in current users and 1.4 (0.4 to 3.2) in users 49-72 months previously compared with never users). No association was found between endometriosis and use of the diaphragm.
  
  
  CONCLUSIONS
  Oral contraceptives seem to temporarily suppress endometriosis. Endometriosis may be diagnosed late in women using intrauterine devices as pain and bleeding occur with both.
authors.affiliation: Department of Public Health and Primary Care, Radcliffe Infirmary, Oxford.
authors.forename: M P
authors.initials: MP
authors.lastname: Vessey
authors.forename: L
authors.initials: L
authors.lastname: Villard-Mackintosh
authors.forename: R
authors.initials: R
authors.lastname: Painter
mesh_terms: D000328:Adult; D000367:Age Factors; D015331:Cohort Studies; D003274:Contraceptive Devices, Female; D003276:Contraceptives, Oral; D004715:Endometriosis / Q000453:epidemiology*; D004739:England / Q000453:epidemiology; D005193:Family Planning Services; D005260:Female; D006801:Humans; D010298:Parity; D010386:Pelvic Neoplasms / Q000453:epidemiology*; D012307:Risk Factors; D013997:Time Factors
chemical_list: D003276:Contraceptives, Oral