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In Vitro Fertilization (IVF) In Vitro Fertilization (IVF), an assisted reproductive technology (ART) in which one or more eggs are fertilized outside a female's body. This technique has been used extensively in animal embryological research for decades, but only since 1978 has it been successfully applied to human reproduction. In human reproduction the process involves stimulation of the growth of multiple eggs by the daily injection of hormone medications. (It is also possible to conduct IVF without the use of the hormone medications; a single egg would develop and be retrieved.) The eggs are recovered by one of two methods: sonographic egg recovery, the more common of the two, which uses ultrasound guidance to retrieve the eggs, or oocytes; or laparoscopic egg recovery, in which retrieval is made through a small incision in the abdomen. Once the eggs are retrieved, they are placed in a special fluid medium, then semen that has been washed and incubated is placed with the eggs and left for approximately 18 hours. The eggs are removed, passed into a special growth medium, and then examined about 40 hours later. If the eggs have been fertilized and developed normally, the embryos are transferred to the woman's (or a surrogate's) uterus. Typically, multiple embryos are transferred to increase the likelihood of pregnancy. If more than four eggs develop into embryos, the donor may have the option of cryopreserving the remaining embryos for thawing and replacement in a later IVF cycle. (Cryopreservation is used to minimize the risk of multiple gestations [twins, triplets, etc.] if more than four embryos are replaced.) Following egg transfer, progesterone injections may be administered daily to the recipient. The probability of viable pregnancy is approximately 20 percent with one IVF cycle. Similar techniques are also available. In gamete intrafallopian transfer (GIFT), the technique is similar to IVF, but the harvested eggs and sperm are placed directly into the fallopian tubes, with fertilization occurring in the woman's body. In zygote intrafallopian transfer (ZIFT), the procedure is similar to GIFT, but the beginning-stage embryos (zygotes) are placed directly in the fallopian tubes. With super ovulation uterine capacitation enhancement (SOURCE), the woman receives daily hormone medications to stimulate the growth of multiple eggs. Once the eggs have reached the right stage, intrauterine inseminations are done using the partner's specially treated sperm. Donor oocyte programs are available in some places; donated eggs are used by women unable to use their own eggs to achieve pregnancy. Assisted reproductive technology is used to retrieve eggs from donors and replace embryos in the recipient. Definiton taken from, Microsoft® Encarta® Online Encyclopedia 2001 http://encarta.msn.com © 1997-2001 Microsoft Corporation. All rights reserved.
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