[Biological effects of GnRH antagonists]. / Les antagonistes du GnRH: effets biologiques.

ABSTRACT

Numerous questions about the efficacy of GnRH antagonists, known for the prevention of undesirable LH surge, have been raised. Al-Inany in 2002 in a meta-analysis, IVF Germany Register and FIVNAT the French data base in 2003, have shown a decrease of the pregnancy rate after antagonists treatment. Among 20761 ART attempts for good prognosis women (<35 years, i.v.f. range 1 or 2) we have compared the clinical and biological parameters after agonists' long protocol versus antagonist treatment. The characteristics of the responses to the stimulation treatment were similar for both groups, whereas the duration of the stimulation and the doses of gonadotrophin used in the antagonist group was lower. The fertilization and embryo development rates were not modified. But we observed a decrease in the number of oocytes retrieved, of embryos obtained and of the pregnancy rate (P < 0.001). These results could be explained by endometrial modifications induced by antagonists but we cannot exclude an impact of oestradiol and LH levels. GnRH antagonists could be an inhibitor of the cell cycle by decreasing the synthesis of growth factors. The interaction of GnRH antagonists and GnRH receptors may compromise the mitotic programme of the cells and induce an alteration of folliculogenesis, embryo quality and implantation. More studies are necessary to understand these results. Using of GnRH antagonists involves specific patient information on the benefits and drawbacks of such treatment before ART.