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IN VITRO FERTILIZATION

In vitro fertilization is the term for a process whereby a mature egg from the female and a sperm from the male are placed in culture media where fertilization can occur. For humans, the first clinically successful in vitro fertilization occurred in 1978. If accomplished, cell division results in six to eight cells in about forty-eight hours, or a blastocyst of 100 cells in about 120 hours. One or more can then be transferred into the uterus with a 20 percent to 60 percent expectation of pregnancy depending on many variables, including age, cause of infertility, and number of fertilized eggs, or pre-embryos, transferred.

Pregnancy rates increase with number of pre-embryos transferred, as do the multiple pregnancy rates. In the United States (1998), 360 clinics conducted 80,634 treatment cycles; 31 percent of deliveries were multiple, compared to 3 percent in the general population.

In vitro fertilization has expanded to include the use of donor eggs, donor sperm, cryopreservation, intracytoplasmic sperm injection (ICSI), and the use of surrogate uteri.