The History of IVF: ZIFT, Zygote Intrafallopian Transfer
Shortly after the GIFT procedure was developed, it was suggested that success rates might improve even more if the oocytes that were placed in the fallopian tube were already fertilized. As a result, ZIFT, or zygote intrafallopian transfer, was developed. The procedure for ZIFT was identical to that of the GIFT procedure with one significant exception. Rather than obtain the eggs and sperm and transfer them back into the woman’s fallopian tube(s) on the same day (GIFT), with ZIFT the eggs and sperm were cultured together in the laboratory for 24 hours to allow fertilization to occur and the fertilized eggs (zygotes) were then transferred into the woman’s fallopian tube(s).
Specifically, oocytes were retrieved transvaginally from the woman’s ovaries. Following the procedure the patient was allowed to go home. Meanwhile, the oocytes were combined with her partner’s sperm and fertilization occurred in the laboratory. On the following day, a laparoscopy was performed and two zygotes were placed in each fallopian tube through its fimbriated end. As with GIFT, patients could only undergo ZIFT if the woman had at least one normal fallopian tube. Pregnancy rates were higher for ZIFT than GIFT because the oocytes placed in the fallopian tubes were already fertilized. The pregnancy rate for ZIFT was approximately 40-45%, while the pregnancy rate for GIFT was approximately 20-25%.
Over time, due to the tremendous advances in the IVF laboratory, pregnancy rates for IVF have become much higher than those that were achieved with ZIFT. In addition, IVF does not require either a laparoscopic procedure, general anesthesia, or the extended use of an operating room, making it safer, less invasive, and less expensive than ZIFT. As a result, ZIFT has become less popular and is now only rarely performed in the United States. One relatively rare exception to this statement is the occasion where a woman’s cervix is severely scarred and transcervical embryo transfer cannot be accomplished. In this situation, consideration for transfer of zygotes into the fallopian tube through the laparoscope remains an option.