Abstract
PURPOSE: Heparin and aspirin (HA) therapy is used for antiphospholipid syndrome (APS)-associated recurrent pregnancy loss (RPL). Low-dose aspirin (LDA) is recommended for thrombophilic predispositions, such as antiphospholipid antibodies that do not completely meet the Sydney classification criteria for APS, protein S deficiency, factor XII deficiency and increased platelet aggregation. However, no established strategy exists for cases where LDA is ineffective. Therefore, this study aimed to identify the characteristics of RPL cases unresponsive to LDA and to determine whether HA is more effective than LDA in such cases. METHODS: A total of 913 LDA-treated pregnancies were categorized into live births and miscarriages, and their characteristics were retrospectively analyzed. RESULTS: The live birth rates following one, two, or three or more LDA therapies were 78.5%, 61.5% and 16.7%, respectively. Live birth rates were significantly lower when lupus anticoagulant (LAC) aPTT was positive but did not qualify as obstetric APS following LDA therapy (birth rates: 33.3%, p = 0.048). Three or more LDA therapies decreased the live birth rate, whereas HA therapy significantly increased the live birth rate (p = 0.0019). CONCLUSIONS: HA therapy is recommended over repeated LDA treatment, particularly when LAC aPTT is positive but does not qualify as obstetric APS.