Association of Antiphospholipid Antibodies with Pregnancy Outcomes in Women with Recurrent Implantation Failure: A Retrospective Cohort Study.

OBJECTIVE: Antiphospholipid antibodies (aPL) may contribute to recurrent implantation failure (RIF) in women undergoing in vitro fertilization (IVF). These antibodies may impair endometrial receptivity and placentation, though evidence remains contradictory due to incomplete aPL data, nonstandardized testing, and inconsistent outcome definitions. To evaluate associations between aPL and pregnancy outcomes in women with RIF following IVF. MATERIALS AND METHODS: In this retrospective cohort study, we analyzed women with 2 or more unexplained implantation failures following IVF. All participants underwent repeated aPL testing-lupus anticoagulant (LA), anticardiolipin (aCL) IgG/IgM, and anti-beta2-glycoprotein I (anti-β2GPI) IgG/IgM-at ≥ 12 weeks intervals. The primary endpoint was the cumulative live birth rate across the first 6 embryo-transfer (ET) cycles. The secondary endpoint comprised per-cycle obstetric outcomes and the influence of prophylactic low-molecular-weight heparin (LMWH). RESULTS: Among 125 women, 26 (20.8%) tested positive for aPL. LA positivity was the most common (59.3%). Across 327 embryo transfer cycles, the live birth rates were comparable between aPL-negative and aPL-positive groups (7.0 vs 7.8%, respectively). Only anti-β2GPI IgM-positive women achieved live births among aPL-positive patients. Cumulative live birth rates after 6 ET cycles reached 38% (95% CI: 15-56) for aPL-negative and 25% (95% CI: 0-46) for aPL-positive women. aPL positivity showed no significant association with live birth (adjusted hazard ratio 0.89, 95% CI: 0.32-2.45, P=0.821). Prophylactic LMWH demonstrated no significant improvements in live birth rates [crude risk ratio (RR) 2.20, 95% CI: 0.73-6.62, P=0.163]. CONCLUSION: Live birth rates were similar between anti-β2GPI IgM-positive and aPL-negative women. No births occurred among LA-positive or aCL-positive patients. LMWH showed no statistically significant benefit. Prospective studies are warranted to confirm these findings (registration number: TCTR20231003007).