OBJECTIVE: This study seeks to examine the prevalence of non-criteria antiphospholipid antibodies (NC-aPLs) in patients experiencing recurrent pregnancy loss (RPL) and to assess their potential association with pregnancy outcomes. METHODS: In this study,247 patients who had experienced at least two pregnancy losses and had been screened for 14 NC-aPLs were recruited between February 2021 and March 2024. Serum levels of NC-aPLs were assessed using line immunoassay (LIA), with the exception of anti-phosphatidylserine/prothrombin IgM (aPS/PT), which was quantified via enzyme-linked immunosorbent assay (ELISA). Pregnancy outcomes were subsequently compared between patients testing positive and negative for NC-aPLs, following the exclusion of individuals with positivity for criteria antiphospholipid antibodies (aPLs), chromosomal abnormalities, uterine anomalies, or thyroid dysfunction. Binary logistic regression analysis was employed to identify factors associated with adverse pregnancy outcomes (APO). RESULTS: The overall positivity rate for NC-aPLs was 38.46% (95 out of 247 participants), with anti-phosphatidylethanolamine (aPE) IgM being the most prevalent subtype, observed in 14.17% of cases. Patients who tested positive for NC-aPLs received more intensive therapeutic interventions, including low molecular weight heparin (LMWH), glucocorticoids, and hydroxychloroquine (HCQ). However, the incidence of APO did not significantly differ between NC-aPLs-positive and NC-aPLs-negative groups (53.68% vs. 46.71%, OR = 1.322, 95% CI 0.791-2.211, p = 0.286). Subgroup analyses did not reveal any significant associations between specific NC-aPLs subtypes [aPE IgM, anti-prothrombin (aPT) IgM, anti-annexin A5 (aAnxA5] IgM) and APO, nor between single and multiple NC-aPLs positivity. Binary logistic regression showed that medicinal degree was associated with lower odds of APO (1-2 drugs: aOR=0.177, 95% CI 0.055-0.569, P = 0.004; 3-4 drugs: aOR = 0.102, 95% CI 0.037-0.283, P < 0.001), while neither single positivity (aOR = 1.553, 95% CI 0.799-3.017, P = 0.194) nor multiple positivity for NC-aPLs (aOR = 1.942, 95% CI 0.798-4.726, P = 0.144) was significantly associated with APO. CONCLUSION: NC-aPLs are detectable in a substantial proportion of patients with RPL. However, this study did not identify any association between NC-aPLs and APO. Patients who tested positive for NC-aPLs received significantly more intensive pharmacological treatment, which was associated with lower odds of APO. This confounding factor may obscure the potential effects of NC-aPLs. Additionally, the limited sample size and the use of a single-time LIA for NC-aPLs detection may introduce bias into the current findings. Further research involving large-scale cohorts and repeated standardized antibody testing is necessary to elucidate the clinical relevance of NC-aPLs and APO.