In Vitro Fertilization
From Encyclopedia of Sex and Sexuality
A baby girl born to Louise Brown in Britain in July 1978 was the first child ever born that was not conceived within her mother’s body. In the United States today approximately one in six couples are unable to have a child at a time of their choosing. The largest single reason for a woman’s inability to become pregnant is that her fallopian tubes have become blocked or damaged. Without normally functioning fallopian tubes, the egg and the sperm are not able to meet normally and pregnancy will not result. Conventional infertility treatments such as microsurgery and laser surgery often have very poor success rates when used to try to repair damaged or blocked fallopian tubes.
In an attempt to better treat this form of infertility, the in vitro—“in glass,” in a laboratory—fertilization process was developed. Simply stated, in vitro fertilization involves removal of one or more eggs from the woman’s body, addition of the husband’s sperm to the eggs in a laboratory dish, and observation in the laboratory for one to two days to document that the eggs have been fertilized by the sperm and are developing normally. The fertilized and divided eggs, now called embryos, are then placed in the wife’s uterus, bypassing the fallopian tubes entirely. Because some of the early experiments mixed the egg and sperm in test tubes, the in vitro fertilization process is sometimes referred to as the “test tube baby” procedure.
Although initially developed for couples in whom the wife had untreatable tubal disease, the use of in vitro fertilization and related technologies have been expanded to treat conditions such as endometriosis, low sperm count or motility in the husband, or cases in which an explanation for a couple’s infertility is not known.
As practiced today, in vitro fertilization involves several steps. Since the pregnancy success rate is raised by increasing the number of embryos placed in the uterus, the first goal is to increase the number of eggs simultaneously developing in a wife’s ovaries. In a normal menstrual cycle, one egg develops within one ovarian follicle (a fluid-filled cyst in which the egg develops). A woman going through in vitro fertilization is treated with drugs normally given to women who do not ovulate. When a normal woman receives these drugs, her ovaries typically overrespond by developing numerous follicles, each containing an egg. The woman’s response to these drugs is monitored by measuring the levels of estrogen produced by the growing follicles and by ultrasound imaging of the ovaries to check the size, number, and growth rate of the follicles. It is not unusual for a woman undergoing in vitro fertilization and receiving these drugs to develop ten, twenty, or even more follicles simultaneously. When it has been determined that the follicles are fully developed, the woman is then given an injection of hCG, a hormone that triggers final maturation of the eggs within the follicles so that they will be able to be fertilized when they are recovered.
Approximately thirty-four hours after the hCG injection, the eggs are removed from the woman’s body. Today this is done with an ultrasound guided aspiration procedure, most commonly performed through the vagina. After giving drugs for relaxation and pain relief, the physician places an ultrasound probe in the vagina to locate the ovarian follicles. A needle is attached to the ultrasound probe and passed through the top of the vagina directly into the ovarian follicles, bypassing the fallopian tubes. The contents of the follicles (including the eggs) are then removed by suction and examined in an adjacent laboratory. The recovered eggs are assessed, rinsed in culture media (a nourishing fluid), and placed in an incubator. The husband then collects a sperm sample. The sperm are washed, suspended in culture media, and lateradded to the eggs. The following morning the eggs are examined for signs of fertilization and, if normally fertilized, are returned to the incubator. The following morning the eggs have divided one or more times and are typically at the two to four cell stage. At this stage they are termed embryos. The embryos are then placed in the woman’s uterus by means of a catheter passed through the cervix. If a pregnancy results, it continues as any normal pregnancy.
At present the success rate of in vitro fertilization is approximately 15 percent. In other words, about one out of seven women who attempt it becomes pregnant. The procedure is expensive, with a cost of $6,000–$8,000 for a single treatment cycle.
The in vitro fertilization process has led to the development of other related treatments. One example is called gamete intra-fallopian transfer (GIFT). This procedure begins in a manner identically with the in vitro fertilization treatment. However, egg recovery is usually done by laparoscopy rather than ultrasound-guided aspiration. Laparoscopy is a surgical procedure in which a lighted telescope is inserted into a woman’s abdomen to allow direct visualization of the tubes and ovaries. After the eggs are removed from the ovaries, they are mixed immediately with sperm. The egg/sperm mixture is immediately placed into the wife’s fallopian tubes rather than allowing fertilization to occur in the laboratory. This procedure is most suitable for couples in whom the wife has normal fallopian tubes and there is some other explanation for the couple’s infertility.
A similar procedure is zygote intra-fallopian transfer (ZIFT). This is a combination of GIFT and in vitro fertilization in which fertilization is carried out in a laboratory but on the day after insemination the early embryo is placed into the woman’s fallopian tube. Again, this requires that the woman have normal fallopian tubes.
In vitro fertilization, coupled with the use of eggs donated by volunteers, can be used to establish a pregnancy in a woman who was born without ovaries or has lost ovarian function at an unusually early age. Finally, micromanipulation procedures such as partial zona (egg membrane) dissection or sperm microinjection can be used where there is a great decrease in the number of sperm or loss of sperm motility. These procedures involve operating on the eggs themselves, making it easier for sperm to penetrate and fertilize them.