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Assisted Reproductive Techniques
Assisted reproductive techniques involve manipulating sperm and eggs in a culture dish (in vitro) with the goal of producing an embryo.
If treatment has not resulted in pregnancy after four to six menstrual cycles, assisted reproductive techniques, such as in vitro fertilization or gamete intrafallopian tube transfer, may be considered. These techniques are more successful in women under age 35. In the United States, more than 47% of cycles of in vitro fertilization in women under 35 result in pregnancy, and 87% of the pregnancies end in live births. In contrast, only about 20% of attempts in women aged 41 to 42 result in pregnancy, and only about 62% of the pregnancies result in live births. For women over 42, using eggs from another woman (donor) is recommended.
Assisted reproductive techniques may result in more than one fetus but are much less likely to do so than fertility drugs. If the risk of genetic abnormalities is high (see Overview of Genetic Disorders : Risk Factors), the embryo can often be tested before it is implanted in the woman’s uterus. This testing is called preimplantation genetic diagnosis.
This technique is used when infertility is due to certain problems with sperm, problems with the fallopian tubes, or abnormal mucus in the cervix and when women have endometriosis, as well as when the cause is unidentified. The technique involves the following:
Stimulating the ovaries: Typically, a woman’s ovaries are stimulated with human gonadotropins, with or without clomiphene. A gonadotropin-releasing hormone agonist or antagonist is often given to prevent ovulation from occurring until after several eggs have matured. As a result, many eggs usually mature. Then, human chorionic gonadotropin is given to trigger ovulation.
Retrieving released eggs: Guided by ultrasonography, a doctor inserts a needle through the woman’s vagina into the ovary and removes several eggs from the follicles. Sometimes the eggs are removed through a small tube (laparoscope) inserted through a small incision just below the navel.
Fertilizing the eggs: The eggs are placed in a culture dish and fertilized with sperm selected as the most active.
Growing the resulting embryos in a laboratory: After sperm are added, the eggs are allowed to grow for about 2 to 5 days.
Implanting the embryos in the woman’s uterus: One or a few of the resulting embryos are transferred from the culture dish into the woman’s uterus through the vagina. The number of embryos implanted is determined by the woman’s age and likelihood of response to treatment.
Additional embryos can be frozen in liquid nitrogen to be used later if pregnancy does not occur. The chances of having a baby with in vitro fertilization depend on many factors, but the woman’s age may be most important.
The greatest risk is having more than one fetus (multiple pregnancy). A multiple pregnancy can cause serious complications in the mother and the newborns. Complications may be related to the pregnancy. For example, the mother may develop high blood pressure (see High Blood Pressure During Pregnancy) or diabetes (see Diabetes During Pregnancy) or have excessive bleeding. The fetuses may die, or the babies may have a low birth weight. Because of these complications, doctors now transfer fewer embryos to the uterus at one time.
Birth defects are more common among babies conceived through IVF. However, experts are unclear whether the reason is related to the technique or to the fertility problems that made IVF necessary. Also, more than 5 million babies have been conceived through IVF, and the overwhelming majority of these babies have had no birth defects.
This technique may be used when other techniques are likely to be unsuccessful or when the problem with sperm is severe. It resembles in vitro fertilization except that only one sperm is injected into only one egg.
Birth defects may be more likely after this procedure, possibly because the procedure can damage the egg or possibly because many men who use this procedure have an abnormal Y chromosome (one of the sex chromosomes), which can affect the development of male reproductive organs. Most birth defects in babies conceived by intracytoplasmic sperm injection involve these organs.
This technique can be used if the fallopian tubes are functioning normally. Eggs and selected active sperm are obtained as for in vitro fertilization, but the eggs are not fertilized with sperm in the laboratory. Instead, the eggs and sperm are transferred to the far end of the woman’s fallopian tube through a small incision in the abdomen (using a laparoscope) or through the vagina (guided by ultrasonography), so that the egg can be fertilized in the fallopian tube. Thus, this technique is more invasive than in vitro fertilization. GIFT is rarely used in the United States because IVF is very successful.
These techniques include the following:
These techniques raise moral and ethical issues, including questions about the disposal of stored embryos (especially in cases of death or divorce), legal parentage if a surrogate mother is involved, and selective reduction of the number of implanted embryos (similar to abortion) when more than three develop.
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