GIFT, ZIFT, AND RELATED TECHNIQUES

This review focuses on the theoretical backgrounds for tubal gamete an d zygote/embryo transfer, as well as the clinical results of gamete in trafallopian transfer (GIFT), which are-compared with other non-fertil ization procedures in infertile women with patent fallopian tubes. Whi le GIFT and zygote intrafallopian transfer (ZIFT) probably result in a more synchronized entry of embryos into the uterine cavity, prospecti ve, randomized studies have not shown these methods to be preferable t o conventional in-vitro fertilization and embryo transfer. Nevertheles s, co-culture with various cell types seems to yield more viable embry os with a high rate of implantation. The promising results with co-cul ture do not seem to be a cell- or species-specific phenomenon. This no n-specific positive or negative conditioning effect of co-culture on e mbryo quality indicates that more optimal culture media for in-vitro f ertilization can probably be devised. The requirements of laparoscopy and general anesthesia with GIFT have prompted the development of simp ler methods based on fertilization in vivo. Various methods of artific al insemination combined with controlled ovarian hyperstimulation yiel d comparable results with GIFT in unexplained infertility. In endometr iosis, GIFT seems to give better results compared with insemination te chniques. Less invasive transcervical gamete and embryo transfer techn iques have now been established, obviating the need for operating thea ter facilities.