Embryo implantation rates in natural and stimulated assisted reproduction treatment cycles in poor responders

Controlled ovarian stimulation Nvith exogenous gonadotrophins and gonaclotrophin-releasing hormone (GnRH) analogues enables the collection of multiple oocytes and subsequent development of' multiple eiribryos. However, interfering with the natural hormonal milieu inay decrease the probability Of Successful erribryo implantation due to effects oil oocytes and/or endonietriurn. In order to provide a fail- comparison of einbryo implantation rates between natural cycles and stimulated cycles, bias caused by the presence of multiple ernbryos available for transfer in stimulated cycles should be avoided. This retrospective Study analysed einbryo implantation rates in cycles in which only a single embryo was available for transfer in 304 women who had poorly respr.mided to ovarian StilnUlation in the previous cycle. Ernbryo implantation rates with different StilnUlation protocols were as fcllows: natural cycle, 20% (6/30); gonadotrophin only, 5.6% (3/54): long GliRH protocol, 3.8% (2/52) co-flare protocol, 1 9% (1/52); microclose flare-up, 15.4% (4/26); GnRH antagonists, 14.4% (13/90). AlthOLI&III the difference was not statistically significant there was a trend towards higher implantation rates with natural cycles in this group of women. Natural cycle IVF may be a reasonable and patient-friendly treatment choice yielding an acceptable Outcome for women who are known or anticipated pool- responders to ovarian stimulation.