RESUMO
INTRODUCTION: the purpose of this retrospective analysis is to compare the efficiency of hCG-induced natural and Clomiphene citrate (CC) cycles in normovulatory patients undergoing frozen embryo transfer (FET). MATERIALS AND METHODS: it was retrospectively conducted in the Dutchspeaking Free University of Brussels and covered the period from April 2003 to August 2006. In particular, 428 day-three FET cycles belonging to the two comparative groups were recruited. Of these FET cycles, 261 were hCG-induced natural and 167 clomiphene citrate-induced cycles. RESULTS: no statistically significant difference was observed in live birth rate between CC and natural group (22.2% versus 22.6%), respectively (P = 0.708). Except for the number of embryos transferred (1.72 ± 0.46 for cc group versus 1.63 ± 0.48 for natural group, p = 0.045), no other parameters seem to influence the outcome. discussion: To our knowledge, this is the first attempt to investigate which of the above mentioned regimens is optimal for normo-ovulatory women in FET cycles. A similar delivery outcome was observed for hCG-induced natural and CC-induced cycles used for endometrial preparation in FET.