text: artificial insemination, the introduction of semen into the vagina or cervix of a female by any method other than sexual intercourse. The procedure is widely used in animal breeding and is used in humans when a male is sterile or impotent or when a couple suffers from unexplained infertility (when the cause of infertility cannot be identified). Impregnation of a woman through artificial insemination may also be used by women or men in same-sex partnerships who wish to produce children of their own.
  Artificial insemination in animals
  The first successful experiment with artificial insemination in animals was performed by Italian physiologist Lazzaro Spallanzani, who in 1780, while investigating animal reproduction, developed a technique for artificial insemination in dogs. This approach was refined in the 1930s in Russia, and the subsequent development of methods for the cryopreservation (preservation through freezing) of semen led to the widespread use of artificial insemination in animals.
  The chief advantage of artificial insemination is that the desirable characteristics of a bull or other male livestock animal can be passed on more quickly and to more progeny than if that animal is mated with females in a natural fashion. Ten thousand or more calves have been produced annually from a single bull through the use of artificial insemination. In the actual procedure used, semen is obtained from a male animal and, after being diluted, is deep-frozen, after which it can be stored for long periods of time without losing its fertility. For use, the semen is thawed and then introduced into the genital tract of a female animal.
  Artificial insemination has been used to facilitate the reproductive success and conservation of threatened or endangered animals. Examples of wild animals that have been successfully impregnated through artificial insemination include big cats (e.g., the tiger, the puma, the cheetah, and the clouded leopard), the white rhinoceros (Ceratotherium simum), and the onager (Equus onager).
  Artificial insemination in humans
  The first recorded experiment with artificial insemination in humans occurred in the late 1700s, when Scottish-born surgeon John Hunter impregnated a women with her husband’s sperm, resulting in a successful pregnancy. In 1884 American physician William Pancoast performed a modified artificial insemination procedure when he injected sperm from a donor into a woman who was under anesthesia. The woman, who was married, gave birth to a baby nine months later and did not know that she had been impregnated with donor sperm. Her husband, whom Pancoast determined was infertile, later found out about the procedure from Pancoast.
  Today artificial insemination in humans is considered a form of assisted reproductive technology. Women impregnated in this way are physically capable of conceiving and bearing children, though they are unable to conceive through sexual intercourse, usually because their husband is sterile or impotent. Fresh semen is obtained from the husband (if he is impotent) or from some other male donor (if the husband is sterile) and is introduced by a syringe into the woman’s vagina or cervix during the middle of her menstrual cycle. The semen can also have been previously frozen and stored in a sperm bank. The technique is reasonably successful in achieving conception and pregnancy.
  This article was most recently revised and updated by Robert Lewis.