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.
Who is IVF for?
In-vitro fertilization is ideal for women who have not been able to become pregnant through regular unprotected intercourse or after 12 cycles of artificial insemination. IVF should be considered as an option if:
- You or your partner have been diagnosed with unexplained infertility
- Other techniques such as the use of fertility drugs or intrauterine insemination (IUI) have been unsuccessful.
- The woman's fallopian tubes are blocked.
IVF patients in the UK are to be offered a groundbreaking treatment that allows fertilization to take place inside the body, rather than in a lab.
Fertility researchers have identified a specific gene signature in the lining of the uterus that could predict recurrent implantation failure during IVF treatment.
IVF Success Rate
The Society of Assisted Reproductive Technologies (SART) reported that the approximate likelihood of IVF cycles resulting in a live birth is:
- 41 to 43 percent for women aged under 35.
- 33 to 36 percent for women aged between 35 to 37.
- 23 to 27 percent for women aged between 38 to 40.
- 13 to 18 percent for women aged 41 and over.
These statistics vary from clinic to clinic.
Research published in CMAJ Open showed that IVF is more successful among women who have sufficient levels of vitamin D. In the study, the pregnancy rates per cycle start were much higher among women with sufficient levels of vitamin D than those with low levels (52.7% vs 34.7% respectively).
Some women may have reactions to the medications that are given during treatment.
The possible side effects of IVF drugs include:
- Difficulty breathing
- Hot flushes
- Enlargement of the ovaries
- Difficulty sleeping
- Abdominal pain.
Bruising is also common as a result of repeated daily injections.
Rarely, the drugs cause ovarian hyperstimulation syndrome (OHSS), this occurs when the ovaries over-respond to the gonadotrophins, resulting in far too many eggs developing in the ovaries, causing severe abdominal swelling and shortage of breath. If OHSS occurs, restarting the whole cycle with a lower dose of gonadotrophin should be considered.
The major cause of pregnancy loss in IVF is chromosomal imbalance in embryos.
Research conducted by the Karolinska Institute in Sweden and published in British Medical Journal, found that IVF is associated with an increased risk of pulmonary embolism (blockage of the lung's principal artery) and venous thromboembolism (blood clots) during the 1st trimester of pregnancy.
When more than one embryo is transferred into the womb there is a risk of multiple pregnancies (an increased chance of producing twins or even triplets).
Carrying more than one baby can:
- Cause babies to be born prematurely or with a low birth weight - around half of all twins are born prematurely.
- Double the mother's risk of developing diabetes
- Significantly raise the mother's blood pressure.
It's for these reasons that the The Human Fertilisation and Embryology Authority (HFEA), UK, recommended that there should only be a single embryo transfer in women who are at a heightened risk of having twins.
Predicting the best embryos for IVF
A technique discussed in the journal Fertility and Sterility in 2012 could hold the promise of predicting the best embryo for IVF which should help cut down multiple pregnancies, according to Cardiff University scientists.
In addition, Yale School of Medicine researchers and colleagues at the University of Oxford identified the chromosomal make-up of a human egg, which allowed them to pick eggs that are healthy enough for a successful IVF cycle.
Finally, scientists have developed a new technology called"time-lapse imaging" which could help triple the chances of a couple having a baby through IVF. The technique can successfully identify which embryos have a high risk of abnormal chromosomes, called "aneuploidy", thus helping the researchers choose which embryos were best suited for implantation.