10.13: In Vitro Fertilization and Artificial Implantation
In vitro fertilization (IVF) is a technique in which egg cells are fertilized by sperm outside the woman's womb. IVF is a major treatment in infertility when other methods of achieving conception have failed. The process involves hormonally controlling the ovulatory process, removing ova (eggs) from the woman's ovaries and letting sperm fertilize them in a fluid medium. The fertilized egg (zygote) is then transferred to the patient's uterus with the intent to establish a successful pregnancy.
The term in vitro, is used, because early biological experiments involving cultivation of tissues outside the living organism from which they came, were carried out in glass containers such as beakers, test tubes, or petri dishes.
While the overall live birth rate via IVF in the U.S. is about 27% per cycle (33% pregnancy rate), the chances of a successful pregnancy via IVF vary widely based on the age of the woman (or, more precisely, on the age of the eggs involved). Where the woman's own eggs are used as opposed to those of a donor, for women under 35, the pregnancy rate is commonly approximately 43% per cycle (37% live birth), while for women over 40, the rate falls drastically - to only 4% for women over 42. Other factors that determine success rates include the quality of the eggs and sperm, the duration of the infertility, the health of the uterus, and the medical expertise. It is a common practice for IVF programmes to boost the pregnancy rate by placing multiple embryos during embryo transfer. A flip side of this practice is a higher risk of multiple pregnancy, which is associated with obstetric complications.
Embryo cryopreservation If multiple embryos are generated, patients may choose to freeze embryos that are not transferred. Those embryos are placed in liquid nitrogen and can be preserved for a long time. There are currently 500,000 frozen embryos in the United States. The advantage is that patients who fail to conceive may become pregnant using such embryos without having to go through a full IVF cycle. Or, if pregnancy occurred, they could return later for another pregnancy.