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Oral contraceptive use and risk of endometriosis. Italian Endometriosis Study Group
F Parazzini1, E Di Cintio, L Chatenoud
1Istituto di Ricerche Farmacologiche Mario Negri and Prima Clinica Ostetrico Ginecologica, Università di Milano, Italy.
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 endometriosis.
Participants:
Eligible for the study were women with primary or secondary infertility (n = 393) or chronic pelvic pain (n = 424), requiring laparoscopy, consecutively observed between September 1995 and January 1996 in 15 obstetrics 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 never 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 relation emerged between duration of oral contraceptive use and risk of endometriosis. In comparison with never users, the OR was 1.8 (95% CI 1.1-3.0) for women reporting their last use of oral contraception < 5 years before interview and 1.5 (95% CI 0.9-2.5) for those reporting their last use > or = 5 years before interview.
Conclusions:
The study suggests that oral contraception is associated with an increased risk of endometriosis but this finding is based on a selected population and cannot generalised to all women with endometriosis.