Reproductive Technologies

Infertility

Infertility is common. In 2002, about 12 percent of women (aged 15–44) in the United States had trouble getting pregnant or carrying a pregnancy to term. Both women and men experience infertility, the causes of which are attributable to women in about one third of cases, to men in about one third of cases, and to a mixture of the two or to unknown factors in the remaining third. A baby's live birth results only after a complicated chain of events. In unassisted pregnancies, mature eggs (ova) release from a woman's ovaries into her fallopian tubes to meet and join with a man's sperm, thus forming an embryo. The fallopian tubes move the fertilized egg into the uterus for implantation, followed by several factors that are necessary for a subsequent live birth. These include having a genetically viable embryo, balanced pregnancy hormones in the woman, and a suitable uterine and cervical anatomy to support the pregnancy to term. Interruption with any of these links results in infertility.

Miscarriage occurs when an established pregnancy stops developing. Premature birth occurs when a live baby is born prior to developing to term. Sterility occurs in women and men who lack the necessary and functioning reproductive organs, including ovaries, fallopian tubes, or uterus in women; or testes, seminal vesicles, and vas deferens in men.

Several factors increase the risk of infertility for women, including age, stress level, diet, physical fitness, body weight, tobacco and alcohol use, sexually transmitted diseases, or general health concerns. Women's infertility often results from problems with ovulation or providing sufficient numbers of genetically healthy eggs for fertilization, and from hormonal dysfunctions that decrease successful ovulation and embryo implantation.

Blocked fallopian tubes may cause infertility and are the result of pelvic inflammatory disease, endometriosis, or ectopic pregnancy (defined as a pregnancy that implants outside the uterus, usually in the fallopian tubes). Anatomical problems with the uterus, including the growth of muscular tumors called fibroids, are a common source of infertility for many women as well. Older women are more likely to become infertile because the number and quality of their eggs declines through time, and they are more likely than younger women to have encountered environmental or other toxins and influences that can negatively affect fertility.

Men's infertility typically results from sperm absence, insufficiency, or problems with quality or mobility. Male factor infertility causes include age; hormone disorders; trauma to or obstruction of the reproductive organs; the use of tobacco, alcohol, and other drugs; exposure to environmental toxins such as pesticides; cancer treatments such as radiation and chemotherapy; and sexual dysfunction.

Assisted Reproductive Technologies

Assisted reproductive technologies (ARTs) are medical and technological interventions designed to overcome infertility and sterility for both women [Page 1072]and men. Artificial insemination (AI), the oldest and most widely used ART, involves the artificial introduction of sperm to the egg. As early as 1790, after first identifying the sperm cell in human reproduction, doctors devised synthetic methods for placing sperm in a woman's uterus.

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