Influence of the morphological aspect of embryos obtained by in vitro fertilization on their implantation rate

In a series of 500 transfers of embryos obtained by in vitro fertilization, we examined the implantation rate of 1356 embryos transferred in utero. The average implantation rate per embryo was 15.1% and remained relatively constant, regardless of the number of transferred embryos per patient. The implantation rate per embryo, in relation to its morphology, was clearly lower when irregular blastomeres and fragments were present in the perivitelline area. Other embryos, regardless of their morphology, had an identical development potential. Analysis of the results of this series demonstrates the difficulty of deter-mining the development potential of all the embryos on the basis of morphological criteria.