Purpose: Coculture, which allows good-quality human blastocysts with good yields to be obtained, has been designed mainly to select the best embryos for transfers.
Methods: In a first attempt during coculture, we have studied by fluorescent in situ hybridization the chromosomic content of the in vitro blocked embryos, using centrometric probes for chromosomes 1, 12, and 18. Close to 37% of the arrested embryos show aneuploidymosaicism.
Results: Freezing cocultured blastocysts gives good recovery rates after transfer (83%). The ongoing pregnancy rates per transfer (19%) are high, and the implantation rate per embryo is 13%. This compares favorably with freezing at an early stage.
Conclusions: We observed that the quality of the endometrium is always the limiting step, as first of all we observed wide variations according to the hormonal preparation of the patients. Moreover the implantation per embryo in the pregnant patients is very high (57%), indicating that most of the losses are directly related to the receptivity of the endometrium.