In gamete intra-fallopian transfer (GIFT), zygote intra-fallopian transfer (ZIFT), or tubal embryo transfer (TET), gametes (eggs and sperm) or early embryos are transferred into the fallopian tube rather than the transfer of embryos into the uterus, as in standard IVF (in vitro fertilization). These procedures are similar to IVF because all steps, from down-regulation to ovarian stimulation to egg retrieval, are identical to IVF. However, several important differences exist. In a GIFT procedure, retrieved eggs and sperm are mixed together and transferred into one or both fallopian tubes (where natural fertilization normally occurs). In a ZIFT procedure, on the other hand, fertilization is allowed to take place in the laboratory just like in standard IVF, however when day-one embryos are formed (called zygotes), they are transferred into the fallopian tube(s) instead of the usual transfer of day-three embryos into the uterus through the cervix, as in IVF. In a TET procedure, day-two embryos are transferred into the fallopian tubes. The transfer of gametes, or early embryos into the fallopian tubes requires a surgical procedure called a laparoscopy.
Current indications for tubal embryo transfer are limited to patients who have cervical obstruction/stenosis or difficult prior trans-cervical embryo transfers, and to patients with multiple prior failed IVF attempts. Tubal transfer is generally not suitable for patients with tubal factor infertility, as at least one normal tube has to be present.
Combined GIFT/IVF or ZIFT/IVF
Combined GIFT/IVF or ZIFT/IVF consists of both a tubal transfer (gametes or early embryos) and a trans-cervical embryo transfer. In these procedures, all known technologies are combined to maximize success rates. After transfer of gametes or day-one embryos into the fallopian tube(s) via laparoscopic surgery (a GIFT or ZIFT procedure), remaining embryos that had been left to develop in the laboratory are transferred into the uterus through the cervix two or three days later, when the embryo is three days old. The advantage of combined treatment is higher pregnancy success rates in couples that have failed multiple prior cycles of standard IVF.