Factors associated with first thrombosis in patients presenting with obstetric antiphospholipid syndrome (APS) in the APS Alliance for Clinical Trials and International Networking Clinical Database and Repository: a retrospective study

Objective: To evaluate the subsequent rate of thrombosis among women with obstetric antiphospholipid syndrome (Ob-APS) in a multicentre database of antiphospholipid antibody (aPL)-positive patients, and the clinical utility of the adjusted Global Antiphospholipid Syndrome Score (aGAPSS), a validated tool to assess the likelihood of developing new thrombosis, in this group of patients. Design: Retrospective study. Setting: The Antiphospholipid Syndrome Alliance for Clinical Trials and International Networking Clinical Database and Repository. Population: Women with Ob-APS. Methods: Comparison of clinical and laboratory characteristics and measurement of aGAPSS in women with Ob-APS, with or without thrombosis, after initial pregnancy morbidity (PM). Main outcome measures: Risk factors for thrombosis and aGAPSS. Results: Of 550 patients, 126 had Ob-APS; 74/126 (59%) presented with thrombosis, and 47 (63%) of these women developed thrombosis after initial PM, in a mean time of 7.6 ± 8.2 years (4.9/100 patient years). Younger age at diagnosis of Ob-APS, additional cardiovascular risk factors, superficial vein thrombosis, heart valve disease, and multiple aPL positivity increased the risk of first thrombosis after PM. Women with thrombosis after PM had a higher aGAPSS compared with women with Ob-APS alone [median 11.5 (4–16) versus 9 (4–13); P = 0.0089]. Conclusion: Based on a retrospective analysis of our multicentre aPL database, 63% of women with Ob-APS developed thrombosis after initial obstetric morbidity; additional thrombosis risk factors, selected clinical manifestations, and high-risk aPL profile increased the risk. Women with subsequent thrombosis after Ob-APS had a higher aGAPSS at entry to the registry. We believe that aGAPSS is a valid tool to improve risk stratification in aPL-positive women. Tweetable abstract: More than 60% of women with obstetric antiphospholipid syndrome had thrombosis after initial pregnancy morbidity.