Reduced plasma fibrinolytic potential in patients with recurrent implantation failure after IVF and embryo transfer.

BACKGROUND Recurrent implantation failure (RIF) following embryo transfer (ET) is a major continuing problem in IVF. Women with haemostatic defects may be at increased risk of miscarriage and preclinical pregnancy loss. The fibrinolytic system is considered, at present, the key to new thrombotic pathogenic mechanisms. Patients with unexplained recurrent miscarriage have an impairment of fibrinolysis, as demonstrated by prolonged clot lysis time (CLT) in association with increased plasma levels of thrombin-activatable fibrinolysis inhibitor (TAFI). In this study, we investigated fibrinolytic potential in patients with RIF. METHODS Three groups of patients were studied: 30 women with RIF (RIF group), 60 patients undergoing a first successful IVF-ET cycle (IVF group) and 60 healthy fertile women (FER group). Plasma CLT was measured using a global fibrinolysis assay. TAFI antigen plasma levels and polymorphisms in the TAFI gene (+505A/G and +1542C/G) were analysed using enzyme-linked immunosorbent assay and allele-specific PCR, respectively. RESULTS CLT was significantly longer (P < 0.0001 and P < 0.0009, respectively) and TAFI antigen levels were significantly higher (both P < 0.0001) in the RIF versus the IVF and FER groups. A direct relationship between CLT and TAFI antigen levels (r = 0.40; P = 0.001) was detected in the whole study population. There were no differences in distribution of TAFI polymorphisms between groups. CONCLUSIONS Patients with RIF have reduced plasma fibrinolytic potential, as shown by a prolonged CLT, and this may be explained, at least in part, by increased TAFI antigen levels.