Objective To study the findings of serum antibodies against annexin V, prothrombin,ph-inositol, ph-acid, ph-ethanolamine, ph-serine, ph-glycerol, cardiolipin, and beta2-glycoprotein I and analyze the trophoblast annexin V receptorsMethods Sera from 156 patients aged 26-41 years with recurrent pregnancy loss (3-7 times) were investigated. Eighty-four fertile healthy women aged 24-38 yearswere included in a control group. ELISA methods were used for detecting a panel of seraanti-phospholipid antibodies. Immunolocalization of annexin V receptors in 143trophoblast specimens of 156 patients was investigated by the immunofluorescencetechnique using Annexin V-FITC, Apoptosis and AnnexinV-CY3 commercial kits.Results Positivity for anti-phospholipid antibodies mainly against ph-serine, ph-ethanolamine, and ph-inositol was found together in 80.8% (126 out of 156 patients),anti-prothrombin antibodies in 12% (18), and anti-annexin V antibodies in 13. 5%(21) women. No significant levels of anti-phospholipid antibodies were found in 6controls. Placenta immunohistopathology also exhibited some changes manifested bythe presence of apoptotic and necrotic cells in trophoblast, and very fewmicrothrombotization in some intervillous spaces.Conclusion Our detailed study demonstrated the prevalence of majority of anti-phospholipid antibodies as a high risk factor for repeated reproductive failure. Verylow microthrombosis in placentas could be explained by the changes ofhaemocoagulation properties out of uterus. Objective To study the findings of serum antibodies against annexin V, prothrombin, ph-inositol, ph-acid, ph-ethanolamine, ph-serine, ph-glycerol, cardiolipin, and beta2-glycoprotein I and analyze the trophoblast annexin V receptors Methods Sera from Eighty-four fertile healthy women aged 24-38 yearswere included in a control group. ELISA methods were used for detecting a panel of seraanti-phospholipid antibodies . Immunolocalization of annexin V receptors in 143trophoblast specimens of 156 patients was investigated by the immunofluorescencetechnique using Annexin V-FITC, Apoptosis and Annexin V-CY3 commercial kits. Results Positivity for anti-phospholipid antibodies mainly against ph-serine, ph-ethanolamine, and ph -inositol was found together in 80.8% (126 out of 156 patients), anti-prothrombin antibodies in 12% (18), and anti-annexin V antibodies in 13.5% (21) women. No significant levels of anti-pho spholipid antibodies were found in 6controls. Placenta immunohistopathology also showed some changes manifested by the presence of apoptotic and necrotic cells in trophoblast, and very few microthrombotization in some intervillous spaces.Conclusion Our detailed research demonstrated the prevalence of majority of anti-phospholipid antibodies as a high risk factor for repeated reproductive failure. Verylow microthrombosis in placentas could be explained by the changes ofhaemocoagulation properties out of uterus.