Impact of the 2023 ACR/EULAR classification criteria in pregnant women with primary antiphospholipid syndrome: insights from a Portuguese cohort

The recently published 2023 ACR/EULAR classification criteria for antiphospholipid syndrome (APS) aim to improve specificity by refining obstetric and serological definitions. We retrospectively reclassified 30 pregnancies fulfilling the Sydney criteria at a Portuguese tertiary multidisciplinary clinic. Twenty-one (70%) met the new criteria, which favored younger patients with high-risk serological profiles (notably lupus anticoagulant and triple positivity). However, obstetric APS cases declined from 8 to 2, excluding women with recurrent early losses or isolated IgM positivity, despite comparable outcomes under prophylactic therapy. These findings highlight that stricter criteria may reduce sensitivity for clinically relevant obstetric APS phenotypes.