The first thrombotic event in purely obstetric antiphospholipid syndrome patients and in antiphospholipid antibody carriers: comparison of incidence and characteristics.

PURPOSE: The long-term risk of thrombosis after pregnancy in women with purely obstetric antiphospholipid syndrome (OAPS) is not well defined. The current study's primary outcome was to evaluate the incidence and characteristics of the first thrombotic event in OAPS, identifying the risk factors for thrombosis in OAPS was its secondary one.

METHODS

Patients with purely OAPS were consecutively enrolled between September 1999 and September 2019. Subjects without a history of pregnancy morbidity or thrombosis but with persistent positivity for one or more antiphospholipid antibodies (aPL carriers) made up the control group. The study groups included 94 OAPS patients and 124 aPL carriers who were matched for clinical and laboratory parameters.

RESULTS

An event rate of 0.49/100 patient years was registered in OAPS patients during a mean follow-up of 8.7 years ± 5.5 SD. Kaplan-Meier survival analysis revealed that the cumulative incidence of thromboembolic events was not significantly different in OAPS patients vs aPL carriers. Arterial thrombosis and cerebrovascular events were the more frequent types of vascular involvement in the two groups. As far as risk factors for thrombosis were concerned, the presence of lupus anticoagulant significantly prevailed in both thrombotic OAPS patients and thrombotic aPL carriers with respect to purely OAPS patients and aPL carriers who did not develop thrombosis (p = 0.01 and p = 0.00, respectively).

CONCLUSION

Just as for aPL carriers, closer monitoring and possibly, a pharmacological prophylaxis should be reserved for OAPS patients at highest risk of developing the first thrombotic event.