Women with Crohn’s disease who were prescribed combination oral contraceptive pills for more than 3 years were 68% more likely to need gastrointestinal surgery than patients who did not use oral contraceptives, according to a national prospective cohort study reported in the June issue of Gastroenterology.

“Our data suggest the importance of carefully evaluating contraceptive options among women with established Crohn’s disease. Future studies should focus on mechanisms by which oral contraceptive use alters risk and progression,” said Dr. Hamed Khalili of Harvard Medical School in Boston and his associates at Harvard and Karolinska Institutet, Solna, Sweden.

Several studies have linked OC exposure to Crohn’s disease itself. But past studies of OCs and Crohn’s disease progression were small, retrospective, or did not adequately ascertain OC exposure, Dr. Khalili and his associates said. To help fill this gap, they identified 4,036 women with Crohn’s disease aged 16-51 years through the Swedish National Patient Register, and ascertained OC exposure by analyzing Sweden’s national prescription database (Gastroenterology. 2016 Feb 23. doi: 10.1053/j.gastro.2016.02.041 ).

During a median follow-up period of 58 months, 482 patients (12%) underwent surgery related to Crohn’s disease, the researchers said. Use of OCs was associated with surgery, but the link only reached statistical significance among women prescribed combination (estrogen-containing) regimens for more than 3 years (adjusted hazard ratio, 1.68; 95% confidence interval, 1.06-2.67) or for more than 900 doses (aHR, 1.60; 95% CI, 1.1-2.34). For each additional year that combination OCs were prescribed, surgery risk rose by nearly 30% (aHR, 1.29; 95% CI, 1.05-1.57). Thus, one extra surgery was needed for every 83 patients who received combination OCs for at least 1 year, said the investigators. Progestin-only prescriptions did not increase the likelihood of needing surgery, and there was no link between current or prior OC exposure and the chances of being prescribed steroids, they noted.

Only one other study has linked OC exposure with Crohn’s disease progression, and it included only 158 patients followed for just a year, Dr. Khalili and his associates said. Exactly how estrogen exposure might trigger Crohn’s disease progression is unclear, but OCs have been linked to changes in intestinal barrier function, increased humoral immunity, and modulation of testosterone levels, which in turn affects cytokine function, they added. “Regardless of the potential mechanism, the effect of OCs on Crohn’s disease progression appears to be related to consistent and long-term use of these medications. Similar patterns of associations have also been reported with other chronic illnesses, such as breast cancer and cardiovascular diseases,” said the researchers. Current OC use itself might not have predicted surgery in the study because about one in four women in Sweden stop taking OCs or switch to a nonhormonal form within 6 months of being prescribed them, they added.

The work was funded by the Crohn’s and Colitis Foundation of America, the National Institute of Diabetes and Digestive and Kidney Diseases, the American Gastroenterological Association, and the American College of Gastroenterology. Dr. Khalili reported receiving consulting fees from Abbvie. One coinvestigator reported consulting relationships with Bayer Healthcare, Pfizer, and Pozen. The other investigators had no disclosures.