Impaired Fertility in Women With Inflammatory Bowel Disease : A National Cohort Study From Sweden

Background and Aims: Inflammatory bowel disease [IBD] has been associated with reduced female fertility. We analyse fertility in a national cohort of women with IBD. Methods: Fertility was assessed in women with IBD aged 15-44 years in 1964-2014, identified from the Swedish National Patient Register and a matched cohort [ratio 1:5]. Patients with indeterminate colitis or inconsistent IBD coding were classified as IBD-unclassified [IBD-U]. Results: The cohorts included 27 331 women with IBD and 131 892 matched individuals. The fertility rate in IBD was 1.52 (standard deviation [SD] 1.22) births per 1000 person-years and 1.62 [SD 1.28] [p<0.001] in matched individuals. Fertility was impaired in all IBD subtypes compared with the matched cohort (hazard ratio Crohn's disease [CD] 0.88, 95% confidence interval [CI] 0.85-0.91; IBD-U 0.86, 95% CI 0.83-0.89; and ulcerative colitis [UC] 0.96, 95% CI 0.93-0.98). Fertility improved during the study period for the IBD cohort except for CD. Parity progression ratio, the proportion of IBD women progressing from one parity to the next compared with the matched cohort, was decreased at all parity levels for CD and IBD-U, but only for multiparous women in UC. Contraceptive usage was higher in IBD, both before and after the diagnosis. Disease severity, bowel resections, and perianal disease in CD affected fertility negatively. Conclusions: Fertility was impaired mainly in women with CD and IBD-U, and less so in UC. During the study period, fertility improved in women with UC or IBD-U. Some results suggest a role of voluntarily reduced fertility