Women with adverse pregnancy outcomes suggestive of obstetric antiphospholipid syndrome (OAPS), but not fulfilling clinical and/or laboratory international classification criteria, are increasingly recognized both in clinical practice and in the literature. This entity is termed non-criteria OAPS (NC-OAPS). It includes clinical scenarios such as two unexplained pregnancy losses, three non-consecutive pregnancy losses, late pre-eclampsia/eclampsia/signs of placental insufficiency, or recurrent implantation failure, as well as positive low-titers of antiphospholipid antibodies (aPLs) and non-classical aPLs. To address the NC-OAPS heterogeneity, a nomenclature proposal was developed. In recent years, retrospective and prospective cohort studies have been designed to clarify the characteristics and outcomes of the different subsets of NC-OAPS. In general, the studies support that NC-OAPS may benefit from treatment with antithrombotic, anticoagulant and/or immunomodulator agents, but several considerations must be made on the robustness and nuances of the scientific evidence. The objective of this review is to critically analyze the available evidence supporting the diagnosis of NC-OAPS, categorize its subsets, and evaluate the impact of treatment strategies on its outcome. We also remark on questions that are still unanswered, such as the lack of consensus on diagnostic criteria or treatment protocols.

Background: The clinical and laboratory features of patients with non-criteria obstetric antiphospholipid syndrome (NC-OAPS), as well as their pregnancy outcomes and ideal treatment are not clearly determined. The aim of this study is to describe the characteristics and outcomes of pregnancies in NC-OAPS and compare them with an obstetric APS (OAPS) cohort. Methods: This is a retrospective study conducted on a cohort of women referred to a high-risk obstetric unit of a tertiary hospital. Women that were classified as having OAPS or NC-OAPS were included and compared in terms of clinical and laboratory characteristics, management, and subsequent pregnancy outcomes. Results: We identified 107 women with 143 pregnancies, 91 with NC-OAPS and 16 with OAPS. There were no differences in demographic features between both groups. Women with NC-OAPS were more likely to have recurrent implantation failure and were predominantly positive for a single antiphospholipid antibody (aPL) subtype. Both groups were treated similarly (low dose aspirin plus low molecular weight heparin in 87.4% of NC-OAPS and 83.3% of OAPS, p > 0.05). Live birth rate (82.4% and 75.0%, respectively, p > 0.05) and adverse pregnancy outcomes (31.6% vs. 37.5%, p > 0.05) in subsequent pregnancies during follow-up were also similar between groups. Conclusions: This study revealed differences in the previous pregnancy morbidity and aPL profiles in women with NC-OAPS and OAPS, although the therapeutic approach and the outcomes of subsequent pregnancies were similar in both groups.

Background: The clinical and laboratory features of patients with non-criteria obstetric antiphospholipid syndrome (NC-OAPS), as well as their pregnancy outcomes and ideal treatment are not clearly determined. The aim of this study is to describe the characteristics and outcomes of pregnancies in NC-OAPS and compare them with an obstetric APS (OAPS) cohort. Methods: Retrospective study conducted in a cohort of women referred to a high-risk obstetric unit of a tertiary hospital. Women that were classified as having OAPS or NC-OAPS were included and compared in terms of clinical and laboratory characteristics, management, and subsequent pregnancy outcomes. Results: We identified 107 women with 143 pregnancies, 91 with NC-OAPS and 16 with OAPS. There were no differences in demographic features between both groups. Women with NC-OAPS were more likely to have recurrent implantation failure and were predominantly positive for a single antiphospholipid antibody (aPL) subtype. Both groups were treated similarly (low dose aspirin plus low molecular weight heparin in 87.4% of NC-OAPS and 83.3% of OAPS, p>0.05). Live birth rate (82.4% and 75.0%, respectively, p>0.05) and adverse pregnancy outcomes (31.6% vs 37.5%, p>0.05) in subsequent pregnancies during follow-up were also similar between groups. Conclusions: This study revealed differences in the previous pregnancy morbidity and aPL profiles in women with NC-OAPS and OAPS, although the therapeutic approach and the outcomes of subsequent pregnancies were similar in both groups.

Women with adverse pregnancy outcomes suggestive of obstetric antiphospholipid syndrome (OAPS) but not fulfilling the clinical and/or laboratory international classification criteria are increasingly recognized both in clinical practice and in literature. This entity is termed non-criteria OAPS (NC-OAPS). It includes clinical scenarios such as two unexplained pregnancy losses, three non-consecutive pregnancy losses, late preeclampsia/eclampsia/signs of placental insufficiency, or recurrent implantation failure, as well as positive low-titers of antiphospholipid antibodies (aPL) and non-classical aPL. Given the heterogeneity of NC-OAPS, an attempt to organize it in subsets was accomplished in the form of a nomenclature proposal. In the last years, retrospective and prospective cohort studies have been designed to clarify the characteristics and outcomes of the different subsets of NC-OAPS. In general, the studies support that NC-OAPS may benefit from treatment, but several considerations must be made on the robustness and nuances of the scientific evidence. In this review we examine the available evidence supporting the diagnosis of NC-OAPS, the features of its different subsets, and the impact of treatment strategies on its outcome, pointing out the questions that are still unanswered.