THE CONTRIBUTION OF EMBRYO CRYOPRESERVATION TO IN-VITRO FERTILIZATIONGAMETE INTRAFALLOPIAN TRANSFER - 8 YEARS EXPERIENCE

In this paper, the authors summarized their experience with embryo cry opreservation over an 8-year period. The results, therefore, reflect t he long-term benefit of embryo cryopreservation to the overall in-vitr o fertilization/gamete intra-Fallopian transfer (IVF/GIFT) programme a nd to the women who had embryos cryopreserved. The stable survival rat e of thawed embryos and pregnancy rate, especially over the past 4 yea rs, suggests that the results can reliably be used to evaluate the eff icacy of the embryo cryopreservation programme. The ongoing pregnancy rate of frozen/thawed embryo transfer is 10.9%, comparable with the on going pregnancy rate of fresh IVF/embryo transfer in our unit over the same period. In addition to those factors known to affect the pregnan cy rate in fresh TVF/GIFT cycles, such as age of the recipients and nu mber of embryos transferred, the major factor affecting the efficacy o f the cryopreservation programme is the number of oocytes retrieved in the initial stimulation cycle, and the number of embryos available fo r cryopreservation. The storage time of cryopreserved embryos will als o have a significant effect on the realization of the total potential of embryo cryopreservation. Overall the contribution of cryopreservati on to our IVF/GIFT programme is substantial, increasing pregnancy rate by 4%, while the greater net benefit, of course, is for the women who had embryos cryopreserved (pregnancy rate increased by 7%), especiall y for those who returned for frozen/thawed embryo transfer cycles (pre gnancy rate increased by 11%).