Oral contraceptive use and risk of endometriosis

Objective To analyse the association between use of oral contraception and risk of pelvic endometriosis. Design We compared use of oral contraception in women with and without endo metriosis. Participants Eligible for the study were women with primary or secondary in fertility (n = 393) or chronic pelvic pain (n = 424), requiring laparoscopy , consecutively observed between September 1995 and January 1996 in 15 obst etrics and gynaecology departments in Italy. Results Out of the 817 women included in the study, 345 had a diagnosis of endometriosis; 164 (47.5%) women with endometriosis and 139 (29.4%) without the disease reported ever using oral contraception. In comparison with nev er users the estimated odds ratios (OR) of endometriosis were 1.8 (95% CI 1 .0-3.3) in current users and 1.6 (95% CI 1.1-2.4) in ex-users. No clear rel ation emerged between duration of oral contraceptive use and risk of endome triosis. In comparison with never users, the OR was 1.8 (95% CI 1.1-3.0) fo r women reporting their last use of oral contraception < 5 years before int erview and 15 (95% CI 0.9-2.5) for those reporting their last use greater t han or equal to 5 years before interview. Conclusions The study suggests that oral contraception is associated with a n increased risk of endometriosis but this finding is based on a selected p opulation and cannot generalised to all women with endometriosis.