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). 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. 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.
