Abstract Background/Aims Patients with inflammatory rheumatic diseases (IRD) have an increased risk of adverse pregnancy outcomes (APO), although the comparative risk of APO in rheumatoid arthritis (RA), juvenile idiopathic arthritis (JIA) and systemic lupus erythematosus (SLE) pregnancies has not been directly compared. Therefore, this study examined pregnancy outcomes (PO) of subjects with RA, JIA, and SLE, who had all received pre-pregnancy counselling to ensure disease control, to identify whether there are any differences in APO between each individual IRD group. Pregnancy outcomes were compared with healthy pregnant subjects lacking IRD, to determine the comparative risk of APO in RA, JIA and SLE pregnancies. Methods A prospective case-controlled study was conducted at University College London Hospital from February 2018 to February 2021. A total of 183 patients were enrolled into the study, consisting of 120 pregnant patients including 60 patients with an IRD (n = 29 RA, n = 12 JIA and n = 19 SLE), 60 pregnant patients without any IRD and 63 non-pregnant patients with IRD (n = 30 RA, n = 12 JIA, n = 21 SLE). Pregnancy outcome data was obtained from all pregnant patients and the individual IRD groups’ outcomes were compared to each other and against outcomes from pregnancies without an IRD. Results Patients were predominantly Caucasian, ranging from 17-45 years of age. Of 111 reported PO, 99.09% (n = 110) resulted in a live birth (n = 27 (100.00%) RA, n = 11 (100.00%) JIA, n = 18 (94.74%) SLE versus n = 54 (100.00%) pregnancies without IRD). Overall, 5.56% (n = 1 SLE pregnancy) resulted in a spontaneous early trimester miscarriage, 6.36% (n = 7) were pre-term births (n = 3 (11.11%) RA, n = 1 (9.09%) JIA, n = 2 (11.11) SLE pregnancies versus n = 1 (1.85%) pregnancy without IRD). No stillbirths/foetal deaths were reported. Only two maternal complications were reported (n = 1 Group B strep infection, n = 1 gestational diabetes in RA pregnancies). In total six foetal complications were observed in four RA (n = 1 each for enlarged kidney, tongue tied, neonatal jaundice and Group B strep infection), n = 1 JIA (tongue tied) and n = 1 SLE (prolapsed cord) pregnancies. In relation to disease activity statuses in pregnancy, the majority of IRD pregnant patients were in remission (n = 42 (73.68%), n = 18 RA, n = 6 JIA and n = 18 SLE), 28 (49.12%) IRD patients had low disease activity (n = 8 RA, n = 2 JIA and n = 18 SLE) and nine (15.79%) had moderate/high disease activity (n = 6 RA, n = 2 JIA and n = 1 SLE). Only two (3.51%) RA patients reported disease flares during pregnancy, whereas no JIA/SLE patients experienced any flares. Conclusion This first prospective case-controlled study of RA, JIA, SLE and healthy pregnancies has identified favourable and comparable PO between IRD pregnancies with good disease control. This study highlights the importance and need for IRD pregnant women to undergo pre-pregnancy counselling and maintenance of disease control during pregnancy to enhance the chances of successful pregnancy outcomes. Disclosure H. Nguyen: None. D.A. Isenberg: Consultancies; AstraZeneca, Merck Serono, Eli Lilly, Servier, Genentech. D.J. Williams: Grants/research support; National Institute for Health Research University College London Hospitals Biomedical Research Centre. I. Giles: Grants/research support; UCB Pharma.