Do Serologic Domains of the 2023 ACR/EULAR Classification Criteria for Antiphospholipid Syndrome Define Distinct Clinical Subgroups During Pregnancy?

To evaluate the clinical applicability of the 2023 ACR/EULAR serologic classification criteria for antiphospholipid syndrome (APS) in a cohort of pregnant women across the APS spectrum, and to assess the association between serologic burden and clinical manifestations, obstetric outcomes, and treatment response, a retrospective cohort study was conducted including 190 pregnant women with persistent antiphospholipid antibody (aPL) positivity. Patients were classified according to the ACR/EULAR serologic criteria into two groups: high serologic burden (≥3 points) and low serologic burden (≤2 points). Clinical, obstetric, therapeutic, and reproductive variables were compared between groups. Nearly one-third of women did not meet the 2023 ACR/EULAR serologic threshold. Although most patients with thrombotic or obstetric APS fulfilled the ACR/EULAR serologic threshold, 28% of women with obstetric APS and 35.3% of those with pregnancy-related morbidity had ≤2 serologic points. Baseline demographic characteristics were similar between groups. Obesity (23.9% vs. 10%; p = 0.04) and obstetric comorbidity (17.9% vs. 5.4%; p = 0.02) were more frequent among patients with higher serologic burden. Rates of obstetric complications were comparable between groups. The most commonly prescribed treatment was low-dose aspirin combined with low-molecular-weight heparin, with no differences according to serologic classification. Live birth rates and adverse pregnancy outcomes were comparable between groups, with favorable outcomes observed in treated pregnancies. Serologic burden as defined by the 2023 ACR/EULAR criteria does not reliably predict obstetric complications, nor identify a clinically more severe subgroup. These findings highlight that clinical judgment beyond formal classification frameworks remains essential when managing pregnant women with antiphospholipid antibodies.