Comparison of Time to Pregnancy in Women With and Without Inflammatory Bowel Diseases.

Background & Aims: Patients are often diagnosed with inflammatory bowel diseases (IBD) during their peak reproductive years. We investigated how IBD affects fertility in a population study of women in Denmark.

Methods: We collected data from the Danish National Birth Cohort, a nationwide study of 92,274 pregnant women recruited from 1996 through 2002. Women who had been actively trying to conceive reported their time to pregnancy through a computer-assisted telephone interview at approximately 16 weeks of gestation. Information regarding IBD was retrieved from the Danish National Patient Register. Using regression models and adjusting for important confounders, we compared time to pregnancy in women with and without IBD.

Results: We calculated time to pregnancy for 74,471 pregnancies in women without IBD, 340 pregnancies in women with ulcerative colitis (UC), and 206 pregnancies in women with Crohn's disease (CD). Compared to non-IBD pregnancies, the adjusted relative risk ratios for time to pregnancy of more than 12 months in women with IBD, UC, and CD were 1.28 (95% CI, 0.99-1.65), 1.10 (95% CI, 0.80-1.51), and 1.54 (95% CI, 1.03-2.30), respectively. The adjusted relative risk ratio was 2.54 (95% CI, 1.39-4.65) for a time to pregnancy of more than 12 months in women who had CD surgery prior to conception vs non-IBD pregnancies. There were too few patients with UC with surgery prior to conception to perform meaningful analyses of this group.

Conclusions: In a study of women with IBD not confounded by voluntary childlessness, we found that women with CD, especially those who have undergone surgery, have a significant increase in time to pregnancy compared to women without IBD. This indicates reduced fertility in subgroups of women with IBD.