The risk of oral contraceptives in the etiology of inflammatory bowel disease: a meta-analysis

Several environmental and genetic factors have been implicated to date in the development of Crohn's disease (CD) and ulcerative colitis (UC). The aim of this study was to provide a quantification of the risk of oral contraceptive pill (OCP) use in the etiology of inflammatory bowel disease.

A literature search was performed to identify comparative studies reporting on the association of oral contraceptive use in the etiology of UC and CD between 1983 and 2007. A random-effect meta-analysis was used to compare the incidence of UC or CD between the patients exposed to the OCP and nonexposed patients. The results were adjusted for smoking.

A total of 75,815 patients were reported on by 14 studies, with 36,797 exposed to OCP and 39,018 nonexposed women. The pooled relative risk (RR) for CD for women currently taking the OCP was 1.51 (95% confidence interval [CI] 1.17-1.96, P= 0.002), and 1.46 (95% CI 1.26-1.70, P < 0.001), adjusted for smoking. The RR for UC in women currently taking the OCP was 1.53 (95% CI 1.21-1.94, P= 0.001), and 1.28 (95% CI 1.06-1.54, P= 0.011), adjusted for smoking. The RR for CD increased with the length of exposure to OCP. Moreover, although the RR did not reduce once the OCP was stopped, it was no longer significant once the OCP was stopped (CI contains 1), both for CD and for UC.

This study provides evidence of an association between the use of oral contraceptive agents and development of IBD, in particular CD. The study also suggests that the risk for patients who stop using the OCP reverts to that of the nonexposed population.