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Zygote Intra-fallopian Transfer (ZIFT)

Zygote Intra-fallopian Transfer (ZIFT)


ZIFT is a technique that combines IVF (In Vitro Fertilization) with a tubal transfer. ZIFT stands for “Zygote Intra-Fallopian Transfer”. Zygotes (i.e., fertilized eggs prior to cell division) are placed via catheter directly into the women’s fallopian tubes. This usually involves a minor surgical procedure that allows you to go home the same day with a minor degree of pain. ZIFT allows fertilized eggs to make their way to the uterus for implantation according to a normal timetable. In contrast, IVF places fertilized eggs (embryos) directly into the uterus. The success rate for ZIFT is higher than with standard IVF, but it can only be performed if the woman has normal fallopian tubes. ZIFT allows couples with serious male factor infertility (e.g., low sperm count, motility or poor quality) the advantage of a tubal transfer when it is combined with the ICSI fertilization procedure. Its advantage over TET is that ZIFT allows for earlier freezing of surplus fertilized eggs that can be used for future attempts at pregnancy. The earlier these fertilized eggs are frozen the more likely they are to survive the thawing process.

In a fertile couple, pregnancy begins with the release of an ovum (egg) from the woman’s ovaries. The egg enters the fallopian tube where it meets with the sperm that have traveled there, following intercourse, from the vagina. The sperm normally fertilize the egg in the fallopian tube. The fertilized egg, now called an embryo, begins to divide and in four days contains many cells. At this time, the embryo moves from the fallopian tube to the uterine cavity where it “floats” for another two to three days. The embryo then implants in the uterine wall with a resultant pregnancy. ZIFT’s major advantages over IVF is that the technique allows the body to nurture the embryos in the more natural environment of the fallopian tubes, while also ensuring that they will enter the uterine cavity at the optimal time for implantation. ZIFT’s advantage over GIFT is the opportunity to observe that fertilization took place.

To prepare her body for the ZIFT procedure the woman receives hormone injections to stimulate development of the ovarian follicles, the sac-like structures that contain the eggs. Administering hormones increases the chances of retrieving many ripened eggs, each one capable of being fertilized and producing a pregnancy. HMG (human menopausal gonadotropin) and recombinant FSH (follicle-stimulating hormone) are the hormones used to stimulate the production of follicles. Up to three or more zygotes are returned to the patient depending on her age and the quality of her eggs. If you have extra zygotes we can freeze them for future attempts at pregnancy via a FET procedure.

To begin a cycle of ZIFT your cycle will begin to be monitored in the previous month. At a certain point you will begin administering a GnRH-Agonist or a GnRH-Antagonist to prevent the premature surge of LH (luteinizing hormone) from triggering ovulation before the eggs can be retrieved. After your menstrual cycle begins you will be examined by transvaginal ultrasound to check the status of your ovaries and pelvis in preparation for your hormone injections. You will also have baseline bloodwork performed at this time. Once you have begun administering the hormone injections (HMG or FSH) approximately four days later you will begin periodic monitoring by ultrasound examination and blood estrogen level. Later that day you will be informed how much HMG or FSH you will be receiving until your next monitoring appointment. The dosage and timing will depend on your age, previous response, and the estrogen level and ultrasound results demonstrated that day. When the monitoring shows the eggs are ripe and ovulation is imminent, an injection of HCG (human chorionic gonadotropin) is administered to the patient to complete the egg maturation process and prepare the eggs for retrieval.

The patient is admitted for the outpatient ZIFT egg retrieval procedure the next day. A semen sample from the husband is obtained while the wife is undergoing the egg retrieval procedure. It is then washed and prepared with the most active and healthy sperm being selected for fertilization of the wife’s eggs. Eggs are retrieved by transvaginal needle aspiration (no surgical incision) via an ultrasound guide while the patient is under light sedation. The aspirated follicular fluid (containing the eggs) is placed in a laboratory dish and the eggs are observed under a microscope for maturity and quality. The eggs are then transferred to a culture dish where they are incubated in a special culture medium. Later, sperm are added to the culture dish so fertilization can take place. Alternatively, the eggs may be fertilized by the ICSI procedure. The patient will be able to go home a few hours later with minimal discomfort.

One day after the egg retrieval procedure the patient returns for the outpatient surgical tubal transfer. The zygotes are loaded into a catheter, which is then placed into the patient’s fallopian tubes through a very small incision in her abdomen while she is under general anesthesia. They are then released into the fallopian tubes where they will go through regular cell division becoming embryos. The embryos are nurtured in the tubes before moving down into the uterus for implantation approximately six days later. ZIFT is intended to be an outpatient procedure and the patient almost always goes home the same day. After she is discharged she will be asked to limit her activity for the next week and get plenty of rest. Progesterone support by IM injection and/or vaginal suppository or cream will begin after your egg retrieval procedure. The hormone progesterone supports a pregnancy by preparing the endometrial lining so it is receptive to implantation. In one week you will have a blood test to check your hormone levels and further instructions for hormone supplementation will be given later that day. Two weeks after the egg retrieval you will have a blood pregnancy test, a quantitative detail HCG. If the test is positive you will continue hormone supplementation for four to eight weeks.

If you do not get pregnant you will discontinue these hormones. You should consider undergoing another cycle in the future as subsequent cycles would also have a high pregnancy rate. Another option is to go through a FET if your cycle yielded extra zygotes for freezing. An advantage of ZIFT to older women is the shorter time period the fertilized eggs remain outside the body. In general, older women have more fragile eggs that are much more susceptible to damage in the in vitro environment. By returning their fertilized eggs to the natural and protective environment of the body sooner, we can limit the potential for damage to the fertilized eggs and increase the odds for a successful implantation. Contact one of our clinics for more information or to arrange a consultation appointment to see if ZIFT or one of our many other procedures will help you fulfill your dream of parenthood.

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