GIFT, ZIFT, and related techniques

This review focuses on the theoretical backgrounds for tubal gamete and zygote/embryo transfer, as well as the clinical results of gamete intrafallopian transfer (GIFT), which are compared with other non-fertilization procedures in infertile women with patent fallopian tubes. While GIFT and zygote intrafallopian transfer (ZIFT) probably result in a more synchronized entry of embryos into the uterine cavity, prospective, randomized studies have not shown these methods to be preferable to conventional in-vitro fertilization and embryo transfer. Nevertheless, co-culture with various cell types seems to yield more viable embryos with a high rate of implantation. The promising results with co-culture do not seem to be a cell- or species-specific phenomenon. This non-specific positive or negative conditioning effect of co-culture on embryo quality indicates that more optimal culture media for in-vitro fertilization can probably be devised. The requirements of laparoscopy and general anesthesia with GIFT have prompted the development of simpler methods based on fertilization in vivo. Various methods of artificial insemination combined with controlled ovarian hyperstimulation yield comparable results with GIFT in unexplained infertility. In endometriosis, GIFT seems to give better results compared with insemination techniques. Less invasive transcervical gamete and embryo transfer techniques have now been established, obviating the need for operating theater facilities.