The use of long- and short-acting forms of gonadotrophin-releasing hormone analogues in women undergoing oocyte donation.

Evidence accumulated in in-vitro fertilization (IVF) cycles suggests that the use of long-acting forms of gonadotrophin-releasing hormone analogues (GnRHa) for pituitary desensitization may impair the outcome of IVF as compared to classical short-acting formulations. Whether the negative effects are directed against the corpus luteum, the endometrium, or both is unknown. However, the presence of high affinity binding sites for gonadotrophin-releasing hormone (GnRH) in the human endometrium suggests a possible role of these analogues on this target organ, affecting embryo implantation. In the present study, we tested direct effects of two different forms of GnRHa on implantation using the ovum donation model. Patients were prospectively allocated to one of the three study groups: the short-acting form of the analogue leuprolide acetate (group I; n=64), the long-acting form of the same analogue (group II; n=58), and the long-acting preparation of the analogue tryptorelin (group III; n=61). A total of 68 cycles of embryo transfer was carried out in group I, whereas 67 were performed in group II and 65 in group III. Cancellation rates were respectively 18.1, 17.3 and 18.8% because of bleeding while being on the waiting list for anonymous oocyte donation. The number of oocytes donated, fertilization rates and embryos replaced in each group were similar. As a result, pregnancy rate per transfer was 38.2, 49.3 and 44.6% respectively. Implantation rates per embryo replaced were respectively 13.4, 19.1 and 17.0%. These data suggest that the use of a long-acting form of GnRHa provides success rates similar to the short-acting preparations, resulting in more convenient medication for patients with ovarian function included in ovum donation programmes.