The Effect of Disease Activity on Birth Outcomes in a Nationwide Cohort of Women with Moderate to Severe Inflammatory Bowel Disease

Background: Active inflammatory bowel disease (IBD) during conception and pregnancy may increase the risk of adverse birth outcomes. Former studies have examined heterogeneous groups of women with varying degrees of IBD severity. We aimed to examine the effect of active IBD on birth outcomes in a more homogeneous group of women with a moderate to severe disease course. Since in Denmark, moderate to severe IBD is an indication for use of anti-tumor necrosis factor-alpha therapy, we examined all women who used anti-tumor necrosis factor therapy during pregnancy. Methods: We identified a nationwide cohort of 219 singleton pregnancies in women treated with anti-tumor necrosis factor-alpha therapy during pregnancy (2005-2014). Pregnancies with clinical disease activity (65.8%) constituted the exposed cohort and pregnancies without disease activity constituted the unexposed (34.2%). Disease activity scores were supported by levels of fecal calprotectin. Outcomes included low birth weight, preterm birth, and congenital anomalies. Results: In women with IBD, disease activity was associated with adjusted odds ratio of low birth weight and preterm birth; 2.05 (95% confidence interval, 0.37-11.35) and 2.64 (95% confidence interval, 0.85-8.17), respectively. In those with clinical moderate to severe disease activity, the odds ratio for preterm birth was 3.60 (95% confidence interval, 1.14-11.36). In women with ulcerative colitis and disease activity, 19.5% had a child with low birth weight and 29.3% gave birth preterm. Conclusion: In women with moderate to severe IBD, 66% experienced disease activity during pregnancy. In those with the highest degree of disease activity, the risk of preterm birth was increased 3 to 4 folds. The proportion of adverse birth outcomes was high, particularly among women with ulcerative colitis and disease activity.