IVF stands for in vitro fertilization. The IVF process is the fertilization of egg cells by sperm performed outside of the woman’s body. The Latin root of the term, in vitro, is translated as ‘in glass.” The earliest biological experiments were done in Petri dishes, test tubes, and glass beakers.
Today, the term “in vitro” is used to designate any biological procedure that is performed outside of the body where it would normally occur. This would be in contrast to a biological procedure that is done to cultivate tissue while still inside of the body, called “in vivo.” The commonly used term of “test tube babies” started back in the early days of IVF research and is still with us today. In actuality, doctors use the less deep Petri dishes instead of the taller test tubes and beakers.
When is IVF Used?
In vitro fertilization is used when a woman
is unable to conceive in the normal manner, which can be due to many
Fallopian tube problems can prevent, or hinder, the release and proper delivery of the egg. Some male fertility issues involve abnormally shaped sperm that, due to their rounded heads, are unable to penetrate the woman’s egg. In these situations, the in vitro process is used in conjunction with intracytoplasmic sperm injection, or ICSI, where the sperm is directly injected into the harvested egg. This same combination of processes is also used in cases where the male has a very low sperm count.
IVF is also commonly used in cases of sperm or egg donation. A woman who has passed through menopause can use a donated egg that has been fertilized in vitro and is implanted in her uterus, to carry and give birth to a baby. Often, the in vitro fertilization process is combined with another process that detects the existence of genetic disorders. These testing procedures are called preimplantation genetic haplotyping (PGH) and preimplantation genetic diagnosis (PGD).
How is IVF Done?
As we have discussed, the IVF procedure is often accompanied by other complimentary procedures. Because of this, there is not a single set of procedural steps. These many other complimentary procedures make what would otherwise be a very low success rate, a very viable tool in the arsenal of fertility doctors. By itself, the IVF procedure consists of taking the contents of a woman’s uterus or fallopian tubes after she had ovulated in a normal manner. The eggs are then introduced to the intended sperm and reinserted in the woman’s uterus. Researchers have found many ways to improve the rate of success for in vitro fertilization. Some of these methods are:
Hyperstimulation of the Ovary is one of the most common procedures used in conjunction with IVF. In this process, fertility drugs are used in a regimen to increase the production of a woman’s eggs. These medications are usually administered by injection on a daily basis for about 2 weeks. The ovarian hyperstimulation is responsible for a better success rate when the eggs are harvested. These fertility medications must be completed with strict supervision by qualified medical doctors to avoid complications that could be life-threatening.
Harvesting the eggs, or egg retrieval, is accomplished with the use of a transvaginal technique that is known as transvaginal oocyte retrieval. A needle is guided by ultrasound to reach the ovaries by piercing the wall of the vagina. The entire process of retrieval commonly runs around twenty minutes and generally harvests somewhere between 10 and 30 eggs. Approximately a day and a half before the retrieval is attempted, a “trigger shot” injection of human chorionic gonadotropin (HCG) is given to the patient to induce the final maturation process.
The Fertilization and Incubation Process of IVF
A Petri dish is prepared that includes a culture medium, and the egg and sperm are introduced to it using a ratio of approximately 1:75,000. The mixture is incubated for eighteen hours, during which time the egg fertilization should occur. At this point, the egg that has been fertilized will have 2 visible pronuclei. This fertilized egg is then moved to a special growth promoting medium, and this new mixture will be left to incubate for approximately 2 days, at which point the egg should exhibit 6-8 cells. The culture mediums can be either artificial or a layer of cells that had been taken from the lining of the patient’s uterus. In the cases where artificial medium are used, this artificial culture medium is changed regularly. Sometimes a procedure called gamete intrafallopian transfer is used. In this process, an egg and sperm are retrieved, combined, and then reinserted into one of the fallopian tubes to allow fertilization to take place there. This is technically an in vivo procedure.
The Embryo Transfer
In Europe, it is common for the embryo to be transferred to the uterus in about 2 days. In Australia, Canada, and the United States, doctors often wait for up to 5 days before making the transfer, especially if there are still multiple good embryos at that point. Research in this area has proved that the transfers done closer to 5 days into their maturation process had a much higher pregnancy success rate. With the additional couple of days, doctors are able to select the best and most mature embryo to transfer. It is also at this time that methods such as PGD are used to detect genetic problems. Selecting the best embryo to transfer greatly adds to the birth rate success.