Prevalence of Antiphospholipid Antibody Syndrome Among Patients with Recurrent Pregnancy Loss: Impact of the Revised 2023 ACR/EULAR Antiphospholipid Syndrome Criteria

Objectives: Current guidelines recommend systematic screening for rheumatic diseases (RDs), including antiphospholipid syndrome (APS), in patients with recurrent pregnancy loss (RPL). However, these recommendations are based on limited evidence, as data on the prevalence of RD in this specific population remain scarce. In particular, the impact of the recent update to the ACR/EULAR classification criteria for APS on the prevalence of RD among RPL patients has yet to be clarified. To address these gaps, this study aims to (i) assess the impact of the 2023 ACR/EULAR APS classification criteria in patients with recurrent pregnancy loss (RPL); and (ii) analyze the prevalence of RD in these patients. Methods: We conducted a retrospective cohort study at Rennes University Hospital. From January 2010 to December 2021, all patients referred to the Clinical Immunology Department for RPL were included. Patients were eligible if they had undergone a full RPL evaluation, according to guidelines. Results: We included 165 women with RPL. APS according to the Sydney criteria was found in 24 (14.5%) patients. No significant differences in obstetric history or clinical signs were observed between APS-positive and APS-negative individuals. Only two patients fulfilled the updated 2023 APS criteria, resulting in 163 (98.8%) patients being classified as having unexplained recurrent pregnancy loss (uRPL). Among them, 108 had a new pregnancy following uRPL, resulting in 87 (81%) live births and 21 (19%) recurrent miscarriages. We did not identify any prognostic factor associated with subsequent pregnancy outcomes, including the patients’ antiphospholipid biological profile. We found a prevalence of non-APS RD of only 2.4% in the study population, including systemic lupus erythematosus, rheumatoid arthritis, and Behçet’s disease. Conclusions: APS was identified in 14.5% of the patients based on the former Sydney criteria and 1.2% according to the revised criteria. The lack of clinical differences between APS and non-APS patients aligns with previously reported limitations of the Sydney criteria in accurately identifying aPLA-related RPL. According to the rarity of APS as per the updated criteria, future large collaborative trials will be needed to further characterize APS-related RPL patients and to determine the best treatment strategy for future pregnancies.