Combined Obstetric and Thrombotic Complications Are Associated with Features Suggestive of an Immune-Enriched Phenotype Among Women with Thrombotic Antiphospholipid Syndrome (APS).

Background/

Objectives

To determine whether obstetric antiphospholipid syndrome (oAPS) among women with primary thrombotic APS (tAPS) defines a distinct immunologic phenotype or influences thrombotic characteristics and recurrence risk.

Methods

This predefined subgroup analysis was conducted within a multicenter retrospective cohort study of 663 patients with persistent antiphospholipid antibody (aPL) positivity and objectively confirmed thrombosis. The present analysis included 295 women with primary tAPS and a history of pregnancy. Participants were classified as oAPS or non-oAPS according to the revised Sydney criteria. Demographic, clinical, obstetric, immunologic, and hematologic features at baseline were compared. Univariable and multivariable logistic regression analyses were performed to identify predictors of oAPS and determinants of arterial versus venous thrombosis.

Results

Of 295 women, 115 (39.0%) met oAPS criteria. ANA positivity (33.0% vs. 19.0%, p = 0.008), triple aPL positivity (46.0% vs. 29.1%, p = 0.003), and severe thrombocytopenia (22.8% vs. 13.3%, p = 0.035) were more frequent in oAPS. In multivariable analysis, ANA positivity remained independently associated with oAPS (adjusted OR 1.94, 95% CI 1.05-3.56; p = 0.033), whereas triple aPL positivity and thrombocytopenia did not remain independently significant after adjustment. Thrombotic phenotype and recurrence rates were similar between oAPS and non-oAPS groups. Obstetric history was not associated with arterial events; hypertension was the strongest predictor of arterial thrombosis (adjusted OR 2.61, p < 0.001).

Conclusions

In primary tAPS, oAPS is associated with features suggestive of an immune-enriched phenotype, particularly ANA positivity, without evidence of a distinct thrombotic phenotype or increased recurrence risk. Integration of obstetric and immunologic features may help guide risk stratification and hypothesis generation for future studies.