Background: Women with inflammatory bowel diseases (IBD) often receive biologics to maintain remission during pregnancy. Aims: To assess maternal and neonatal outcomes in patients with IBD treated with ustekinumab (UST) during pregnancy. Methods: In a multicentre, prospective, cohort study, we recruited women with IBD treated with UST during pregnancy between 2019 and 2021. Outcomes were compared among patients treated with UST, anti-tumour necrosis factor α, (anti-TNF) and non-UST, non-anti-TNF therapies. UST-treated patients were matched 1:2 to controls according to age, body mass index and parity. Newborns were followed up to 12 months. Results: We recruited 129 pregnant patients: UST 27; anti-TNF 52; non-UST, non-anti-TNF 50 (thiopurine or mesalazine 30, no therapy 20); Crohn's disease 25 (96.9%). Overall, pregnancy, neonatal and newborn outcomes were satisfactory, with no significant differences among patients treated with UST, anti-TNF and non-UST non-anti-TNF agents for obstetrical maternal complications [UST 3 (11.5%), anti TNF 12 (23.1%), non UST, non-anti-TNF 4 (8.2%), p = 0.095], pre-term delivery [1 (4.3%), 9 (18.4%), 4 (5.7%), p = 0.133], low birth weight [1 (4.2%), 5 (10.2%), 4 (8.3%), p = 0.679], or first year newborn hospitalisation [2 (9.1%), 4 (8.2%), 3 (6.1%), p = 0.885]. Conclusion: Pregnant patients with IBD treated with UST demonstrated favourable pregnancy and neonatal outcomes that were comparable with those in patients treated with anti-TNF or other therapy. Data are reassuring for patients with IBD and their physicians when considering UST during pregnancy.