Objective To examine the chance of live births and adverse birth outcomes in women with ulcerative colitis (UC) and Crohn's disease (CD) compared with women without inflammatory bowel disease (IBD) who have undergone assisted reproductive technology (ART) treatments.

Methods This was a nationwide cohort study based on Danish health registries, comprising all women with an embryo transfer during 1 January 1994 through 2013. The cohorts comprised 1360 ART treatments in 432 women with UC, 554 ART treatments in 182 women with CD and 148 540 treatments in 52 489 women without IBD. Our primary outcome was live births per ART treatment cycle. We controlled for multiple covariates in the analyses. Our secondary outcomes were adverse birth outcomes.

Results The chance of a live birth for each embryo transfer was significantly reduced in ART treatments in women with UC (OR=0.73, 95% CI 0.58 to 0.92), but not significantly reduced in the full model of ART treatments in women with CD (OR=0.77, 95% CI 0.52 to 1.14). Surgery for CD before ART treatment significantly reduced the chance of live birth for each embryo transfer (OR=0.51, 95% CI 0.29 to 0.91). In children conceived through ART treatment by women with UC, the OR of preterm birth was 5.29 (95% CI 2.41 to 11.63) in analyses including singletons and multiple births; restricted to singletons the OR was 1.80, 95% CI 0.49 to 6.62.

Conclusions Our results suggest that women with UC and CD receiving ART treatments cannot expect the same success for each embryo transfer as other infertile women. Women with CD may seek to initiate ART treatment before needing CD surgery. Increased prenatal observation in UC pregnancies after ART should be considered.