Background: Janus kinase (JAK) inhibitors are effective for the treatment of inflammatory bowel disease (IBD). However, this class of medications is not recommended during pregnancy or breastfeeding based on animal data suggesting teratogenesis and recent reports of transmammary transfer after maternal ingestion, raising concerns for immune system development in babies exposed to these drugs., Methods: We present the case of a patient with IBD treated with a JAK inhibitor who decided to continue the medication throughout her pregnancy and during breastfeeding. This is the first reported case of a detailed immunologic profile in a baby exposed to tofacitinib in utero and during lactation., Results: A 30-year-old female with ulcerative colitis with previous exposure to vedolizumab and infliximab achieved complete remission with tofacitinib therapy. The patient became pregnant after 5 months of JAK inhibitor therapy and decided to continue tofacitinib during pregnancy and while breastfeeding. The patient delivered a healthy offspring with no congenital malformations, a normal detailed immunologic profile, and subsequent safe provision of the live oral rotavirus vaccine., Conclusions: This case highlights the importance of individualized counseling for patients of childbearing age who are candidates for JAK inhibition. Those who are pregnant or breastfeeding with refractory disease may have limited medical therapeutic options. Ongoing effective therapy for IBD resulted in complete disease remission in the mother and favorable outcomes in the infant. Further, an in-depth infant immunological assessment can lead to specific vaccination recommendations in exposed infants., Competing Interests: K.E.-S.: Consultant, advisor, and speaker for Abbvie, AstraZeneca, Ferring, Janssen, Pfizer, Sandoz, Takeda. L.E.M.-F.: Honoraria: The Academy for Continuing Advancement in Healthcare Education. K.L.N.: Consultancy and/or speaking honoraria: AbbVie, Amgen, Bristol-Myers Squibb, Ferring, Fresenius Kabi, Janssen, Eli Lilly, Pendopharm, Pfizer, Satisfai Health, Takeda; Research funding: Janssen, Pfizer, Takeda and the Helmsley Trust. R.P.: Consultant for: Abbott, AbbVie, Abbivax, Alimentiv (formerly Robarts), Amgen, Arena Pharmaceuticals, AstraZeneca, Biogen, Boehringer Ingelheim, Bristol-Myers Squibb, Celgene, Celltrion, Cosmos Pharmaceuticals, Eisai, Elan, Eli Lilly, Ferring, Galapagos, Fresenius Kabi, Genentech, Gilead Sciences, Glaxo-Smith Kline, JAMP Bio, Janssen, Merck, Mylan, Novartis, Oppilan Pharma, Organon, Pandion Pharma, Pendopharm, Pfizer, Progenity, Prometheus Biosciences, Protagonist Therapeutics, Roche, Sandoz, Satisfai Health, Shire, Sublimity Therapeutics, Takeda Pharmaceuticals, Theravance Biopharma, Trellus, Viatris, Ventyx, UCB. Speaker’s Fees for: AbbVie, Amgen, Arena Pharmaceuticals, Bristol-Myers Squibb, Celgene, Eli Lilly, Ferring, Fresenius Kabi, Gilead Sciences, Janssen, Merck, Organon, Pfizer, Roche, Sandoz, Shire, Takeda Pharmaceuticals. Advisory Boards for: AbbVie, Alimentiv (formerly Robarts), Amgen, Arena Pharmaceuticals, AstraZeneca, Biogen, Boehringer Ingelheim, Bristol-Myers Squibb, Celgene, Eli Lilly, Ferring, Fresenius Kabi, Genentech, Gilead Sciences, Glaxo-Smith Kline, JAMP Bio, Janssen, Merck, Mylan, Novartis, Oppilan Pharma, Organon, Pandion Pharma, Pfizer, Progenity, Protagonist Therapeutics, Roche, SandozShire, Sublimity Therapeutics, Takeda Pharmaceuticals, Ventyx. C.C.: No conflicts of interest. C.H.S. MBBS (Hons), MSc, FRACP: Advisory Boards: Janssen, Abbvie, Takeda, Pfizer, Fresenius Kabi, Bristol-Myers Squibb, Pharmascience, Lilly; Speaker: Janssen, Abbvie, Takeda, Pfizer, Fresenius Kabi, Lilly; Funding: ACHRI (Alberta Children’s Hospital Research Institute), Crohn’s and Colitis Canada, CIHR (Canadian Institutes of Health Research), Calgary Health Trust; DSMB: New South Wales Government Health., (© The Author(s) 2024. Published by Oxford University Press on behalf of Crohn's & Colitis Foundation.)