To Örebro University

BACKGROUND & AIMS: Inflammatory bowel disease (IBD) is linked to reduced female fertility, but it is unclear how fertility rates vary by histological disease activity.

METHODS: Nationwide IBD cohort of Swedish women aged 15-44 years. We examined fertility rates during periods with vs. without histological inflammation (n=21,046; follow-up: 1990-2016) and during periods with vs. without clinical activity (IBD-related hospitalization, surgery, or treatment escalation) (n=24,995; follow-up: 2006-2020). Accounting for socio-demographics and comorbidities, we used Poisson regression to estimate adjusted fertility rate ratios (aFRRs) for live-births conceived during 12-month-periods of histological inflammation (vs. histological remission) and 3-month-periods of clinically active IBD (vs. quiescent IBD).

RESULTS: During periods with vs. without histological inflammation, there were 6.35 (95%CI=5.98-6.73) and 7.09 (95%CI=6.48-7.70) live-births conceived per 100 person-years of follow-up, respectively, or one fewer child per fourteen women with 10 years of histological inflammation (aFRR=0.90; 95%CI=0.81-1.00). In women with histological inflammation fertility was similarly reduced in ulcerative colitis (UC, aFRR=0.89 [95%CI=0.78-1.02]) and Crohn's disease (CD, aFRR=0.86 [95%CI=0.72-1.04]). Clinical IBD activity was associated with an aFRR of 0.76 (95%CI=0.72-0.79) or one fewer child per six women with 10 years of clinical activity. Fertility was reduced in clinically active UC (aFRR=0.75 [95%CI=0.70-0.81]) and CD (aFRR=0.76 [95%CI=0.70-0.82]). Finally, also among women with clinically quiescent IBD, histological inflammation (vs. histological remission) was associated with reduced fertility (aFRR=0.85 [95%CI=0.73-0.98]).

CONCLUSIONS: An association between histological and clinical activity and reduced female fertility in CD and UC was found. Notably, histological inflammation was linked to reduced fertility also in women with clinically quiescent IBD.