Pregnancy and Live Birth Rates Over Time in Women With Inflammatory Bowel Disease: A Population-Based Cohort Study.

Background: Inflammatory bowel disease (IBD) negatively affects fertility and fecundity. We aimed to determine longitudinal trends in and factors that affect pregnancy rates in women with ulcerative colitis (UC) and Crohn's disease (CD). Methods: Women in the University of Manitoba IBD Epidemiology Database aged 15 to 45 were identified between 1992 and 2018 and matched up to 10 non-IBD controls. Pregnancy and live birth rates were compared between women with and without UC or CD stratified by time-period, disease duration and maternal age at conception. Incidence rate ratios (IRR) with 95% confidence intervals (CI) were calculated. Poisson regression was used to adjust these rates for year of pregnancy, disease duration, maternal age, severity of IBD, and prior IBD-related surgery. Results: Compared to controls, women with UC had lower rates of pregnancies (IRR 0.91, 95% CI: 0.82-0.99) and women with CD had lower rates of pregnancies (IRR 0.85, 95% CI: 0.79-0.93) and live births (IRR 0.83, 95% CI: 0.75-0.92). Although rates of pregnancies and live births were significantly lower in women with UC and CD compared to controls prior to 2010, there appeared to be no differences between the two groups after 2010. Prior intestinal surgery and active disease at conception appeared to lower pregnancy rates in women with UC and CD, respectively. Conclusion: This study demonstrates that women with IBD have lower pregnancy rates compared to those without IBD, though these differences are no longer evident after 2010. Factors that continue to reduce these rates include prior colectomy and underlying disease activity.