In vitro fertilization (IVF) is the most common and most effective type of assisted reproductive technology (ART) to help women become pregnant.
The IVF procedure involves fertilizing an egg outside the body, in a laboratory dish, and then implanting it in a woman's uterus.
In a normal pregnancy a male sperm penetrates a woman's egg and fertilizes it inside her body after ovulation - when a mature egg has been released from the ovaries. The fertilized egg (now an embryo) then attaches itself to the wall of the uterus (womb) and begins developing into a baby. This is known as natural conception.
However, some women are unable to become pregnant through natural or unassisted conception and have to undergo fertility treatment to become pregnant.
If less expensive fertility techniques do not work, some women may decide to opt for IVF. According to the American Society for Reproductive Medicine, about 1% of U.S. infants are conceived through IVF. To date, IVF has contributed to approximately 5 million births.
IVF has been used since the late 1970's. On 25 July, 1978, the first test-tube baby, Louise Brown, was born. Robert Edwards and Patrick Steptoe, who were both responsible for the birth, are considered to be the pioneers of IVF.
In 2010, Robert Edwards was awarded the 2010 Nobel Prize in Physiology or Medicine "for the development of in-vitro fertilization".
First IVF baby using next generation DNA sequencing born - in July, 2013, an American couple had the first IVF baby to be born as a result of next generation DNA sequencing, a new way of screening embryos that improves IVF success rates and significantly reduces the cost of treatment. DNA sequencing technology helps doctors screen embryos created by IVF to identify those most likely to lead to successful pregnancies.
IVF - The procedure
IVF techniques may differ depending on the clinic, but usually involves the following steps:
IVF step one - Suppressing the natural menstrual cycle
Women are given a drug (generally in the form of a daily injection) for about two weeks, which suppresses their natural menstrual cycle.
IVF step two - Super ovulation
Fertility drugs containing the fertility hormone FSH (follicle stimulating hormone), are administered to the woman. FSH makes the ovaries produce more eggs than normal. Vaginal ultrasound scans can monitor the process in the ovaries.
IVF step three - Retrieving the eggs
The eggs are collected through a minor surgical procedure known as "follicular aspiration". A very thin needle is inserted through the vagina and into an ovary. The needle - which is connected to a suction device - sucks the eggs out. This process is repeated for each ovary.
Researchers at the University of Birmingham, England wrote in the journal Human Reproduction, that doctors should collect around 15 eggs from a female's ovaries in one cycle if they want her to have the highest chance of giving birth to a child after ART.
IVF Step four - Insemination and fertilization
The eggs that have been collected are placed together with male sperm and kept in a environmentally controlled chamber. After a few hours the sperm eventually enters the egg. However, sometimes the sperm is directly injected into the egg, this is known as an intracytoplasmic sperm injection (ICSI).
Frozen sperm as good as fresh sperm - researchers from Washington University School of Medicine in St. Louis reported in PLoS ONE that frozen sperm retrieved through testicular biopsy is as effective as fresh sperm in achieving successful IVF pregnancy.
The fertilized egg divides and becomes an embryo. At this point some centers offer pre-implantation genetic diagnosis (PGD) which can screen an embryo for genetic disorders (a somewhat controversial technique not always used).
Either one or two of the best embryos are selected for transfer.
The woman is then given progesterone or hCG (chorionic gonadotrophin) to help the lining of the womb receive the embryo.
IVF step five - Embryo transfer
Sometimes more than one embryo is placed in the womb. It is important that the doctor and the couple wishing to have a child discuss how many embryos should be transferred. Generally speaking, doctors should only transfer more than one embryo if there are no ideal embryos available.
The transfer is done via a a thin tube (catheter), which goes up the vagina and into the womb, successfully transferring the embryo. When the embryo sticks to the lining of the womb healthy embryo growth begins.
How IVF works - video
This 3d animated video explains how IVF works.
On the next page we look at who IVF is for, the success rates of IVF, the risks and some research that may, one day, assist scientists with predicting the best embryos for IVF.