In vitro fertilization (IVF) is a laboratory procedure in which egg cells are fertilized outside a woman’s body and then transferred to her uterus. Among the first successful IVF procedures are those that produced a child in England in 1978 and another in the U.S. in 1981. Now this treatment is used worldwide in infertility cases when other conception methods have not been successful.
The procedure actually involves several steps that occur over an approximate three week period. All steps are outpatient procedures. The first involves hormonal stimulation of the women’s ovarian follicles, usually consisting of about 10 days of injections. As many as four or five medications are given to the patient during the in vitro process prior to implantation of the egg.
At the proper point in the cycle, prior to ovulation, the physician retrieves egg cells from the ovary in a transvaginal technique. The patient is normally sedated, either consciously or under general anesthesia; the procedure takes about 20 minutes. In the lab, the eggs and the provided semen incubate together for approximately 18 hours. If necessary, an egg is injected with a single sperm. Once fertilized, the egg is placed in a special growth medium, where it remains for about 24 hours or until it has reached a 6 to 8 cell stage.
The highest quality embryos, generally no more than four, are transferred to the uterus by means of a thin, plastic catheter that the physician inserts through the vagina and cervix. During the waiting period to determine whether the embryo has implanted, a woman may receive a hormone, progesterone, to keep the uterus lining thickened. About two weeks after the embryo transfer, a blood test will determine whether the procedure was successful.
The success rate for each in vitro fertilization cycle is around 20 to 30%. Many factors affect its success rates, including patient age, sperm and egg quality, reproductive health, duration of the infertility, and medical expertise. Because multiple embryos are often transferred, the risk of multiple births is the major complication in IVF. Another risk factor is over-stimulation of the ovaries. Although some studies indicate an increased risk of birth defects in children conceived in this way, other studies do not.
Some couples decide to freeze embryos that are generated but not transferred during in vitro fertilization. The embryos can survive in liquid nitrogen. Other couples chose to dispose of any unused embryos.