Concentration of leukaemia inhibitory factor (LIF) in uterine flushing fluid is highly predictive of embryo implantation.

BACKGROUND: There is strong evidence that locally secreted cytokines control the implantation process and can cause implantation failure. Uterine flushing fluids were analysed to determine their concentrations of leukaemia inhibitory factor (LIF) and tumour necrosis factor (TNF). METHODS AND RESULTS: We began by flushing the uterine cavities of 33 infertile patients on day 26 of two consecutive cycles. The concentrations of LIF (by enzyme-linked immunosorbent assay) and TNF (by bioassay) were significantly correlated during these cycles (r = 0.762, P = 0.0001 and r = 0.822, P = 0.001 respectively) and hence reliable. Then, after a reference flushing of 30 infertile patients, we followed the outcome of their first consecutive cycle of ovarian stimulation, which preceded either IVF or intrauterine insemination. A total of 10 patients became pregnant. The median concentration of LIF was 0 pg/ml (range: 0-177) and of TNF was 0 U/ml (range: 0-6.17) among those who became pregnant, and 203 pg/ml (range: 0-1620) and 2.14 U/ml (range: 0-16) respectively among those who did not. The LIF concentration was significantly lower in the pregnant group (P = 0.0013). CONCLUSION: A low concentration of LIF in the uterine flushing fluid at day 26 was predictive of subsequent implantation. Use of this procedure should increase the number of IVF attempts yielding successful pregnancies and also lead to corrective therapies.