Gamete and zygote intrafallopian transfers and related techniques.

Until recently, most authors reported superior results (ie, higher implantation and pregnancy rates) with gamete intrafallopian transfer (GIFT) and zygote intrafallopian transfer (ZIFT) compared with results using in vitro fertilization-embryo transfer (IVF-ET). According to these investigators, the advantages of tubal over uterine transfer are related mainly to a stable tubal environment and a more appropriate arrival time of the embryo into the uterine cavity. However, more recently, the use of IVF-ET has been increasingly extended to etiologies other than tubal infertility. Indeed, the recent simplification of this technique and the achievement of pregnancy rates comparable to those obtained with tubal transfers have seriously questioned the value of ZIFT and any other type of tubal embryo transfer. As discussed in this review, the results obtained with various transfer procedures in nontubal infertility must still prove ZIFT to be a more effective procedure than IVF-ET. Efforts to develop transcervical methods of transfer to the tube have not translated into higher pregnancy rates than those with IVF-ET. On the other hand, laboratory conditions appear to affect embryos in ways not corrected by the tubal milieu. Negative effects of laboratory conditions on embryos are confirmed by differences in results between GIFT and ZIFT that are accentuated with age. The results obtained with GIFT in patients 40 years of age and older seem to emphasize not only the high compliance of the endometrial receptivity but also the relevance of the biologic potential of the embryos in the process of implantation at this age.