To examine the association between use of oral contraceptive pills (OCPs) and the risk of developing inflammatory bowel diseases (IBD), in a modern cohort.

A prospective nested case-control study across sites in the Asia-Pacific region was conducted; involving female IBD cases and asymptomatic controls. Subjects completed a questionnaire addressing questions related to OCP use. Primary outcome was the risk of development of IBD of those exposed to OCP versus non-exposure. Secondary outcomes were development of Crohn's disease (CD) versus ulcerative colitis (UC), and whether age of first use of OCP use may be associated with risk of IBD.

Three hundred and forty-eight female IBD cases (41% CD, median age: 43 years) and 590 female age-matched controls were recruited. No significant association was found between OCP use and the risk of IBD (odds ratio [OR], 1.65; 95% confidence interval, 0.77–3.13; P=0.22), CD (OR, 1.55) or UC (OR, 1.01). The lack of association persisted when results were adjusted for age and smoking. IBD cases commenced OCP use at a younger age than controls (18 years vs. 20 years, P=0.049).

In this large cohort of subjects from the Asia-Pacific region, we found a modest but not significantly increased risk of developing IBD amongst OCP users.