How does use of oral contraception affect the risk of developing endometriosis?

Updated: May 10, 2021
  • Author: G Willy Davila, MD; Chief Editor: Michel E Rivlin, MD  more...
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Findings from the prospective Australian Longitudinal Study on Women's Health of 9,585 women (age at trial onset, 18-23 y) indicated that, regardless of fertility status, previous exposure to oral contraceptive pills (OCPs) reduced the risk of a subsequent diagnosis of endometriosis among parous women but increased the risk among nulliparous women. [39]

Relative to women who never used OCPs, the hazard ratio (HR) for endometriosis among women with up to 5 years of OCP use before diagnosis was 1.8 in nulliparous women compared with 0.41 in parous women. In those with a history of OCP use for 5 years or longer, the HR was 2.3 in nulliparous women and 0.45 in parous women. [39] The investigators suggested a possible reason for the twofold increased risk of endometriosis among the nulliparous women may have been early noncontraceptive use of OCPs.

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