Background Postpartum depression is a psychiatric illness that occurs after the birth of a child and affects 12.5% of women in the United States (1) and 17.2% of women globally [2]. Women of reproductive age with rheumatic diseases (RD) are at increased risk of clinical depression [3]. However, research examining postpartum depression in women with RD is scarce. Objectives We examined postpartum depression among women with axial spondyloarthritis (axSpA), rheumatoid arthritis (RA), or psoriatic arthritis (PsA) compared to a matched population without RD in the United States. Methods A retrospective analysis using data from the 2013-2018 IBM MarketScan Commercial Claims and Encounters Database was conducted. Pregnant women with axSpA, RA, or PsA were identified, and the date of delivery was used as the index date. We restricted the sample to women ≤ 55 years with continuous enrollment ≥ 6 months before date of last menstrual period and throughout pregnancy (baseline period). Each patient was matched with four individuals without RD on: 1) maternal age at delivery; 2) prior history of depression; and 2) duration of depression before delivery. The outcome of interest was a diagnosis of depression within one year of the index date. Cox frailty proportional hazards models adjusting for sociodemographic and clinical characteristics in the baseline period were used to estimate the crude and adjusted hazard ratios and 95% confidence interval (CI) of incident postpartum depression among women with axSpA, RA, or PsA (axSpA/RA/PsA group) compared to the matched non-RD comparison group. Results Overall, 2,667 women with axSpA, RA, or PsA and 10,668 patients without any RD were included. The average age at baseline was 33 years (SD: 5.0), and nearly two in five women were older than 35 years. The median follow-up time in days was 256 (Interquartile range (IQR): 553) and 265 (IQR: 564) for the axSpA/RA/PsA and matched non-RD comparison groups. Development of postpartum depression was more common in the axSpA/RA/PsA group relative to the matched non-RD comparison group (axSpA/RA/PsA group: 17.2%; matched non-RD comparison group: 12.8%; adjusted hazard ratio: 1.22 [95% CI, 1.09 – 1.36). Factors such as pre-existing comorbidities, maternal complications during pregnancy, and antidepressants use at baseline were associated with development of postpartum depression. Conclusion The rate of postpartum depression is significantly higher in women of reproductive age with axSpA, RA, or PsA compared to those without RD. Results from this study demonstrate that strategies to monitor postpartum depression after delivery in patients with RD must be developed and implemented to assure prompt referral of affected mothers for appropriate evaluation and treatment. References [1]Bauman BL, Ko JY, Cox S, D'Angelo DV, Warner L, Folger S, et al. Vital signs: postpartum depressive symptoms and provider discussions about perinatal depression—United States, 2018. Morbidity and Mortality Weekly Report. 2020;69(19):575. [2]Wang Z, Liu J, Shuai H, Cai Z, Fu X, Liu Y, Xiao X, Zhang W, Krabbendam E, Liu S, Liu Z, Li Z, Yang BX. Mapping global prevalence of depression among postpartum women. Transl Psychiatry. 2021 Oct 20;11(1):543. doi: 10.1038/s41398-021-01663-6. Erratum in: Transl Psychiatry. 2021 Dec 20;11(1):640. [3]Skinner-Taylor CM, Perez-Barbosa L, Corral-Trujillo ME, Perez-Onofre I, Barriga-Maldonado ES, Cardenas-de la Garza JA, et al. Anxiety and depression in reproductive age women with rheumatic diseases. Rheumatol Int. 2020;40(9):1433-8. Acknowledgements This work was supported by the charitable contribution to UMass Memorial Foundation from Timothy S. and Elaine L. Peterson. Disclosure of Interests None Declared.