[GnRH antagonists and embryo implantation potential].

In several trials, the GnRH antagonists regimens have been associated with a slightly lower pregnancy and implantation rate than the established GnRH agonist protocols. Several embryo classification systems have been developed to grade embryo quality, and a cumulative embryo score has been proposed to predict pregnancy. The cumulative embryo score is based on a 4-point embryo score in which all cleaved embryos were assigned 1 point and 1 additional point was added for each of the following features: absence of fragmentation (or fragmentation involving <20% of the embryonic surface), absence of irregularities in blastomere size or shape, and four-cell stage (regardless of cell morphology). This cumulative embryo score is highly correlated with embryo implantation rates. In a non prospective study concerning 641 IVF cycles with oocyte retrieval, pregnancy and implantation rates were statistically lower in the group of patients treated with GnRH antagonist. The explanation of this difference is the indication in IVF cycles: the women with tubal infertility and/or endometriosis had lower pregnancy and implantation rates in IVF cycles if an antagonist was administrated. There was no difference between the 2 groups in ICSI cycles. Subsequently, in IVF cycles, antagonist should not be administrated to women with tubal infertility and/or endometriosis.