Research & Education
Health Care Professionals
Patients
Assisted Reproductive Technologies (ART)
Several procedures can be used to unite sperm and eggs, thus bypassing altogether some of the factors causing infertility. Collectively, these procedures are referred to as assisted reproductive technologies (ART). Although most couples do not require these procedures to conceive, ART provides hope for those who do not respond to other therapies. The simplest ART procedures use various medicines to stimulate ovulation and laboratory procedures to prepare sperm cells for insemination at the time of ovulation.
Advanced ART procedures involve the use of various hormones to stimulate the growth of as many oocytes as possible. This multiple oocyte development increases the chances for fertilization and, subsequently, pregnancy. The most common advanced ART procedures include:
- In vitro fertilization (IVF)
- Gamete intrafallopian transfer (GIFT)
- Zygote intrafallopian transfer (ZIFT)
In Vitro Fertilization (IVF)
In vitro fertilization (IVF) was the first ART developed and is the most commonly used ART procedure. It is effective in overcoming a variety of infertility problems, particularly tubal problems or marked sperm problems. The IVF patient undergoes a regimen of hormonal stimulation to entice the ovaries to produce multiple eggs, which are retrieved with ultrasound guidance. The eggs or oocytes are inseminated in the culture dish and fertilization is confirmed the next day. The embryos are incubated in the laboratory for an additional two days and transferred back to the female partner's uterus. The non-surgical transfer is accomplished by loading the embryos into a small catheter, threading the catheter through the cervical canal, and depositing the embryons into the uterus. As many as four embryos are routinely trasferred back to the uterus. Transferring multiple embryos has improved IVF success rates, as it has been generally observed that only one out of three embryos will implant. The incidence of twinning is thus increased somewhat while the risks of triplets or quadruplets remains low. Couples having more embryos than intended for transfer have the option of freezing additional embryos for future use.
Gamete Intrafallopian Transfer (GIFT)
Gamete Intrafallopian Transfer (GIFT), developed in 1984, is another ART procedure used to assist infertile couples. The procedure is based on the speculation that in some cases of infertility, the sperm and egg do not arrive at the site of fertilization–the fallopian tubes. Gamete Intrafallopian transfer (GIFT) involves the stimulation of ovaries to produce multiple eggs, which are retrieved with ultrasound guidance, and transfer of these harvested eggs combined with sperm to the fallopian tubes by laparoscopy immediately following collection. Up to four of the highest quality eggs are transferred during the procedure. The remaining collected eggs may be fertilized in vitro and resulting embryos can be cryopreserved for later use. However, GIFT can only be used in patients with healthy fallopian tubes. In recent years, with the improvement in pregnancy rates from IVF, the extra surgical risk and cost of the GIFT procedure limit its use to a select few number of patients.
Zygote Intrafallopian Transfer (ZIFT)
Zygote intrafallopian transfer (ZIFT) or pronuclear stage embryo transfer (PROST) combines aspects of both IVF and GIFT. Protocols for ovarian stimulation are identical to those used for IVF and GIFT. Eggs are collected and fertilized by the partners sperm in the laboratory. What makes ZIFT different from IVF is that the embryo is placed into the woman's fallopian tube via laparoscopy instead of the uterus. As with GIFT, the ZIFT procedure has limited use.
There are several procedures associated with ART techniques:
- Pituitary desensitization
- Cryopreservation
- Micromanipulation
Pituitary Desensitization
When discussing ART therapies with the physician, the couple may hear the term pituitary desensitization. This condition is medically induced and shuts down the cells of the pituitary gland that make hormones to affect the ovary. A desensitized pituitary gland minimizes the chance of a premature LH surge. Such a surge usually results in a canceled ART cycle because the eggs necessary to continue the procedure cannot be retrieved.
Cryopreservation
Many ART centers now have the ability to preserve embryos not used in a particular ART cycle, for future use. Once embryos are frozen and stored, they remain viable for long periods of time. About half of frozen embryos will survive thawing and can be transferred. Cryopreservation enables some embryos to be used in the ART cycle and some to be stored for future use in a natural cycle (a cycle without hormonal stimulation). Cryopreservation may also lower the cost of subsequent ART procedures because the first few stages (ovarian stimulation, egg retrieval) do not have to be repeated when the frozen embryos are used.
Micromanipulation
In men with radically reduced sperm numbers or immotile and abnormal sperm, the success of IVF has been limited. When sperm quality is severely compromised (i.e. poor count, poor motility or poor survival), microsurgical intervention, such as gamete micromanipulation, may be used. This procedure involves IVF combined with a microscopic procedure directed at increasing the chance of fertilization. It is especially effective for men with very low sperm count or in couples who have not found success with routine IVF.
Two of the more promising procedures include:
- Intracytoplasmic sperm injection
- Assisted hatching
Intracytoplasmic Sperm Injection (ICSI)
ICSI is a micromanipulation procedure involving the injection of a single sperm into an egg (oocyte) to allow fertilization to occur in the laboratory. After fertilization, the embryo is allowed to grow for a short period of time before it is transferred to the uterus. The procedure was originally developed in Belgium, has proved to be an effective assisted fertilization technique for patients that produce low number of motile sperm in the ejaculate or sperm that fail to fertilze oocytes following conventional in vitro insemination.
Procedure:
- A motile sperm is captured in a glass injection needle
- The oocyte is held by a glass holding pipet through gentle suction.
- The injecton needle pierces the oocyte and the single sperm is injected into the cytoplasm.
- The injection needle is withdrawn from the oocyte and the sperm decondenses for normal fertilization to proceed.
Assisted Hatching
This is a form of embryo micromanipulation whereby a hole is artificially produced in the embryo's covering, which may increase the chance of embryo development. Selective assisted hatching may increase the chance of pregnancy in certain patients (for example, women with a history of implantation failure or in women with embryos having a thick zona pellucida).
ART: Summary
Although very few couples undergo advanced assisted reproductive technologies, the success rate has improved steadily since these procedures were introduced in the late 1970s. In most cases, success may require more than one attempt before conception occurs. However, this is true even of normally fertile couples who have at best a 25 percent chance of achieving pregnancy within any given month. With the use of advanced ART procedures, infertile couples have a chance of pregnancy that compares favorably to that of a fertile couple. In fact, ART procedures have resulted in pregnancy rates ranging from five–15 percent for simple methods involving IUI to 35 percent for the more involved GIFT procedure to 25–50 percent for the IVF procedure.
Bookmark this Page
Print this Page
Resize Text
