Combined oral contraceptive-associated venous thromboembolism revealing an antiphospholipid syndrome: International retrospective study of outcomes.

Limitations in the data used to define thromboprophylaxis for patients with antiphospholipid antibodies (aPLAbs) and thrombosis include uncertainties after an initial provoked venous thromboembolic event (VTE). We aimed to study such cases associated with combined oral contraceptive (COC) intake. We retrospectively analysed thrombotic outcomes after a first COC-associated VTE and positive aPLAbs, with a low risk HERDOO2 score, on low-dose aspirin (LDA) secondary thromboprophylaxis, seen from 2010 to 2021 in 3 tertiary referral centres, one in France and 2 in Russia. Data from 264 patients (distal deep vein thrombosis DVT: 62.9 %), cumulating in 1327.7 patient-years of observation, were collected. There were 22 cases of thrombosis: 16 distal DVTs, 3 proximal, 1 pulmonary embolism (PE) and 2 transient ischemic attacks. Recurrence rate was 1.66 per 100 patient-years (p-y; 95 % CI: 0.96–2.33). No major bleeding occurred. Risk factors affecting recurrence-free survival were the time between first COC intake and VTE (p < 0.0001; the shortest, the lower), proximal DVT (p = 0.021), active smoking (p = 0.039), an associated systemic disease (p = 0.043) and circulating monocyte counts (p = 0.001). We observed a low risk of recurrence which was modulated by classical risk factors for VTE. These observational data may provide clues for future randomized controlled trials.