4 INDICATIONS FOR EMBRYO-TRANSFER AT THE BLASTOCYST STAGE

The transfer of blastocysts obtained by co-culture with 'Vero' (Africa n green monkey kidney) cells was offered to infertile couples with the following indications: (i) repeated failure of implantation, (ii) pat ients in whom multiple pregnancies had to be avoided (malformed uterus or risk of descending uterus), (iii) patients where embryo developmen t potential had to be assessed, and (iv) replacement of supernumerary embryos frozen at the blastocyst stage. In the 142 cycles analysed, th e pregnancy rates per transfer were 37.2, 36.3, 13.0 and 13.6% respect ively for the couples with indications i-iv. The respective implantati on rates per blastocyst were 20.0, 16.7, 7.1 and 9.3%. In patients in whom multiple pregnancies had to be avoided, the transfer of a maximum of two blastocysts gave a pregnancy rate per cycle of 23.5%, without any multiple pregnancies. The freezing of supernumerary embryos at the blastocyst stage allowed us to replace them using simple protocols an d to avoid cancellation of the transfer cycles. Embryo co-culture has been found to be an interesting technique for selected indications, ma king available a good number of blastocysts for transfer. The transfer of blastocysts allowed us to reduce the number of embryos transferred per patient and therefore also reduce the rate of multiple pregnancie s (there were no triplet pregnancies in this study). These results nee d to be confirmed by larger, randomized studies with comparisons to co ntrol groups to evaluate the effectiveness of blastocyst transfers.