What is zygote intrafallopian transfer (ZIFT)?
Zygote intrafallopian transfer (ZIFT) is technique in which a woman's egg is fertilized outside the body, then implanted in one of her fallopian tubes. This technique is one of the methods used to overcome infertility, the inability of couples to produce offspring on their own.
This procedure involves the placement of the single-celled embryo or "zygote" directly into the fallopian tube utilizing a laparoscope. The rationale for this procedure is that the zygote is normally fertilized in the fallopian tube and hence
implantation may be enhanced in some cases following ZIFT. As in IVF and GIFT, ZIFT involves ovarian stimulation, monitoring and egg retrieval. Ideally, to ensure the greatest possibility of success, several eggs, or ova, are collected and fertilized at a time. In preparation, the ovaries are stimulated with hormones to release several mature eggs at once. At the optimal time, eggs are collected using one of two retrieval techniques: ultrasound or laparoscopy.
The ultrasound retrieval method is performed in the doctor's office. The doctor places a needle inside a guide which is attached to an ultrasound vaginal instrument. After the patient receives a local anaesthetic, the doctor uses the ultrasound instrument to locate the follicles containing the eggs. Then the doctor gently guides the needle through the vaginal wall and aspirates the fluid containing the eggs into a small tube.
The maleîs sperm are collected, specially prepared, and combined with the eggs in a special medium that contains the nutrients similar to those found in the uterus. After a day, during which fertilization takes place, the fertilized eggs are evaluated, transferred to another dish containing a suitable solution, and allowed to grow. With ZIFT, the embryos are just grown in the lab for a day and are transferred back the day after retrieval. In conventional IVF, the transfer is conducted either three or five days after retrieval. The fertilized eggs, or pre-implantation embryos, are evaluated for normal development and are then transferred into the fallopian tubes using a laparoscope. This procedure may be performed in the office under sedation and local anaesthetic, or in short-stay surgery if an epidural or general anaesthetic is desired.
You may also hear the ZIFT procedure referred to as tubal embryo transfer (TET). Another slight difference between IVF and ZIFT (besides the stage of the transferred embryo) is the location where the embryos are placed in the woman's body. With IVF, the embryos are placed directly into the uterus. With ZIFT, however, the zygotes are placed directly into the fallopian tube. Therefore, a criterion for performing ZIFT is that the female partner has at least one open and functioning fallopian tube.
One disadvantage with ZIFT is that the transfer of the zygote must be performed through a laparoscope. This involves a surgical incision, whereas with IVF, the fertilized eggs are transferred through the vagina without the need for any incisions. Although laparoscopy is a minor surgical procedure, it still adds to the complexity, risk, and cost of the entire process.
ZIFT requires that the woman have at least one functioning fallopian tube. Therefore, ZIFT is not an option in women with infertility caused by tubal problems. However, like IVF, it is possible to determine whether fertilization has taken place. The obvious advantage of ZIFT is that ZIFT uses zygotes, not an egg and sperm mixture.
Essentially GIFT and ZIFT are analogous procedures, however their specific features justify their utilization in different circumstances. Patients with failed GIFT procedures or in cases where there's some doubt about the sperm's ability to fertilize the egg, ZIFT may be a better option than GIFT. With ZIFT, fertilization is documented prior to replacement of the zygote into the fallopian tube. ZIFT may be indicated if additional procedures need to be implemented to fertilize the oocytes such as in cases of severe male factor infertility where ICSI may be necessary.
Also ZIFT may be a preferred alternative if you want to decrease the probability of multiple pregnancy. A few zygotes are selected for fresh transfer depending upon their quality. The number of zygotes transferred seeks to maximize the pregnancy rate without increasing considerably the probability of a multiple pregnancy.