Fertilization Techniques
If treatment has not resulted in pregnancy after four to six menstrual cycles, fertilization techniques, such as in vitro fertilization or gamete intrafallopian tube transfer, may be considered.
In vitro (test tube) fertilization involves stimulating the ovaries, retrieving released eggs, fertilizing the eggs, growing the resulting embryos in a laboratory, and then implanting the embryos in the woman's uterus.
Typically, a woman's ovaries are stimulated with human gonadotropins and a gonadotropin-releasing hormone agonist or antagonist (drugs that prevent ovulation from occurring until after several eggs have matured). As a result, many eggs usually mature. Guided by ultrasonography, a doctor inserts a needle through the woman's vagina into the ovary and removes several eggs from the follicles. The eggs are placed in a culture dish and fertilized with sperm selected as the most active. After about 3 to 5 days, two or three of the resulting embryos are transferred from the culture dish into the woman's uterus through the vagina. Additional embryos can be frozen in liquid nitrogen to be used later if pregnancy does not occur. Despite the transfer of several embryos, the chances of producing one full-term baby are only about 18 to 25% each time eggs are placed in the uterus.
Intracytoplasmic sperm injection may be used with in vitro fertilization to improve the chances that the woman will become pregnant, particularly when the man has a very low sperm count. In this procedure, a single sperm is injected into a single egg. With this procedure, the chances of producing a full-term baby are about the same as those with in vitro fertilization alone.
Gamete intrafallopian tube transfer (GIFT) can be performed 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 the sperm in the laboratory. Instead, the eggs and sperm are transferred to the far end of the woman's fallopian tube through the abdomen (using a laparoscope) or the vagina (guided by ultrasonography), so that the egg can be fertilized in the fallopian tube. Thus, this procedure is more invasive than in vitro fertilization. For each transfer, the chances of producing a full-term baby are about the same as those with in vitro fertilization.
Variations of in vitro fertilization and GIFT include the transfer of a more mature embryo (blastocyst transfer), use of eggs from another woman (donor), and transfer of frozen embryos to a surrogate mother. 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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