Zygote Intrafallopian Transfer, or ZIFT, is a specialized form of Assisted Reproductive Technology (ART) developed to help individuals and couples achieve pregnancy when natural conception has proven difficult. This fertility treatment involves laboratory manipulation of gametes followed by a surgical procedure to place the fertilized egg into the reproductive tract. ZIFT represents an intermediate step between traditional in vitro fertilization and earlier tubal transfer methods, offering a distinct approach to the conception process.
The Underlying Principle of Zygote Intrafallopian Transfer
ZIFT is defined by a two-part process that combines laboratory fertilization with a tubal transfer. The first step involves retrieving eggs and sperm and achieving fertilization in vitro, meaning outside the body in a controlled laboratory setting. This initial step ensures the egg has successfully been fertilized by the sperm, forming a single-celled zygote.
Once fertilization is confirmed, usually within 24 hours, the resulting zygote is transferred into the woman’s fallopian tube. This differs from standard in vitro fertilization, where the developing embryo is typically placed directly into the uterus. The transfer into the fallopian tube allows the zygote to continue its early developmental stages and natural migration toward the uterus. This tubal placement mimics the biological path a naturally conceived embryo would take, potentially allowing for better synchronization with the uterine lining.
When ZIFT is Recommended
ZIFT is typically considered for couples who have experienced unexplained infertility. Confirming fertilization in the lab addresses concerns about whether the sperm and egg are capable of uniting. For ZIFT to be an option, the patient must have at least one healthy and patent fallopian tube, since the transfer relies on the tube to transport the developing embryo to the uterus.
ZIFT may also be suggested in cases involving mild male factor infertility, where sperm quality or quantity is sufficient for fertilization in the lab. Patients who prefer the earliest embryonic development to occur within the natural environment of the fallopian tube might also select ZIFT. However, because the procedure is more invasive and standard in vitro fertilization success rates have improved significantly, ZIFT is performed less frequently today.
Comparing ZIFT, IVF, and GIFT
ZIFT, in vitro fertilization (IVF), and Gamete Intrafallopian Transfer (GIFT) are all ART procedures, distinguished by the location of fertilization and the type of cells transferred. Standard IVF involves laboratory fertilization, and the resulting embryo is transferred directly into the uterine cavity, bypassing the fallopian tubes entirely. This makes IVF suitable even when the fallopian tubes are blocked or damaged.
GIFT is closer to a natural process because fertilization occurs in vivo. With GIFT, the unfertilized gametes (eggs and sperm) are surgically placed into the fallopian tube, where conception is expected to take place. The primary drawback of GIFT is that fertilization cannot be confirmed beforehand, creating uncertainty about the process’s success.
ZIFT combines elements of both. Like IVF, fertilization is confirmed in the laboratory, removing the uncertainty associated with GIFT. However, similar to GIFT, the transfer is made into the fallopian tube, not the uterus. The key difference is that ZIFT transfers a zygote (a fertilized egg), while GIFT transfers gametes (unfertilized eggs and sperm), and IVF typically transfers a developing embryo to the uterus.
The ZIFT Treatment Timeline
The ZIFT cycle begins with controlled ovarian stimulation, where the patient takes fertility medications to encourage the ovaries to produce multiple mature eggs. The development of the follicles is closely monitored over several weeks using blood hormone levels and ultrasound imaging. Once the follicles reach the appropriate size, a trigger injection is administered to prompt the final maturation of the eggs.
Approximately 36 hours after the trigger shot, the eggs are retrieved using a transvaginal ultrasound-guided aspiration procedure. In the lab, these eggs are combined with the partner’s sperm for fertilization, resulting in the formation of zygotes. The next day, the confirmed zygotes are selected for transfer.
The transfer itself is a surgical procedure, typically performed using a laparoscopy, which requires general anesthesia. The physician uses a thin catheter inserted through a small abdominal incision to place the zygotes directly into the fallopian tube. Following the transfer, the patient is monitored for signs of early pregnancy, with a blood test conducted about two weeks later to determine if implantation has occurred.