It’s estimated that around 1 million babies around the world have been conceived using IVF technology. Although it is often unpredictable how many cycles a woman will need to have a successful pregnancy, the success rate is still only around ¼ per cycle. No matter how far the technology of IVF has come, it does still not guarantee that couples will always end up with a baby. However, it still offers higher chances of conceiving than the 20% of fertile of couples who conceive naturally per month.
In Vitro Fertilization cycles often vary between countries and individual fertility clinics. What is causing the couple’s infertility will determine how a cycle is conducted and what treatments are offered. Assisted Reproductive Technology and IVF are a complex science and a “one way fits all approach” doesn’t allow for the enormous individual variation.
This is done just prior to the IVF cycle starting and involves a final check on the woman’s hormone levels. If her follicle stimulating hormone level is already high, this can indicate that any additional hormones to stimulate her ovaries are unlikely to be effective. This is what happens normally during menopause. The clinic may also check her cervix to see if it will allow for the passage of a fine catheter during embryo transfer. Some women need a dilatation of their cervix early in the treatment process.
Suppression of the Ovaries
This is done by using nasal spray or by injections which stop the pituitary gland from producing follicle stimulating hormone. When the levels of FSH are controlled artificially, this makes the collection of follicles an easier process. Artificial stimulation is generally more effective when it is fully monitored and controlled without any underlying hormonal influences from the woman’s body.
Around two weeks after the ovaries have been suppressed no follicles will be visible on the woman’s ovaries. Ultrasound will confirm this, as well as blood tests which indicate the level of estrogen her body normally produces is very low. Follicle Stimulating Hormone can be given via injections. Many women and their partners learn how to give these injections so they don’t need to trek into the fertility clinic each day. Injections, nasal sprays or tablets containing FSH will increase the number of follicles that “ripen” in each menstrual cycle. This enables the clinic to eventually collect and fertilize several eggs – giving a better overall chance of achieving a pregnancy. Care needs to be taken regarding the dose of FSH which is given. Otherwise, hyperstimulation of the ovaries can result and in rare circumstances, this condition can be life threatening. This is why it is necessary for women to be carefully monitored and have regular blood tests and ultrasounds during the ovarian stimulation phase.
Eggs need to be at a final stage of maturation before they can be fertilized. This normally occurs from the action of the Luteinizing Hormone, but in controlled IVF cycles, this doesn’t happen because the pituitary gland is being suppressed. So another hormone-Human Chorionic Gonadotrophin (HCG) is given which helps the eggs progress to the final stages of maturation. Investigations with blood tests and ultrasounds help to know when the eggs are ready for collection.
Egg collection occurs around 36 hours after HCG is given. This is usually done in the operating theatre and when the woman is sedated. This is a painless procedure. A fine needle is inserted through the vaginal wall and into the ovary where the eggs are collected. Around 97% of the time, at least one egg is collected through this process.
Insemination or Fertilization:
Semen needs to be prepared to remove any impurities and for it to be cultured. A few hours after the eggs are collected the sperm and eggs are mixed together and placed back in the incubator. Semen which is fresh or has been frozen can be used in this process however; the process of freezing and storage is complex. An alternative to combining the semen and eggs is to directly inject the egg with the sperm in a process called Intra Cytoplasmic Sperm Injection (ICSI). This procedure is more expensive but can sometimes offer a higher guarantee of success. When the sperm is injected directly, around 60-80% of injected eggs become successfully fertilized. Very careful checking and cross checking of the eggs and sperm is done to ensure they match the couples identity.
This is the very early stage where cell division first begins. This process is watched closely by laboratory staff to ensure that actual fertilization of the egg with the sperm has taken place. When the embryo has divided into at least four cells then it can be transferred into the woman’s uterus. Most commonly, this is around 2 days after fertilization.
The embryos are transferred using a fine plastic tube or catheter which is inserted through the woman’s vagina and cervix up into the uterus. Transfer is usually done with the aid of ultrasound, so that it is clear exactly where in the uterus the tip of the catheter is sitting. Depending on the clinic, there is a limit to how many embryos are transferred. Currently, the usual number is two. Many couples imagine that the embryo is going to rattle blindly around inside the uterus unless it quickly secures itself firmly to the uterine wall. But the reality is that the uterine walls are in contact with each other and the embryo is injected in exactly the right place to support implantation.
This can be a very stressful time, especially for women who feel they need to be extra careful about any activity. But in normal conception, physical activity does not influence implantation success and this is the same for IVF. After implantation, women are given Progesterone which helps to support the early pregnancy by creating a more suitable uterine lining. A blood test is taken between 12-14 days after transfer, however, pregnancy tests are not considered reliable until sixteen days after egg collection.
What Influences the Chances of IVF Success?
- Maternal age plays an important role in the outcome of IVF. Women over the age of forty have a lower than average rate of IVF success and are also more likely to miscarry. It is a fact that IVF mothers tend to be older than mothers who conceive naturally. The optimal age for IVF is between the early twenties and before turning forty.
- Women who have had a healthy pregnancy before and have not needed IVF to help them conceive have more success.
- Being within a healthy weight range also helps. Carrying too much fat or conversely, being underweight does not help to support conception. Being overweight also increases the likelihood of developing gestational diabetes, hypertension and having complications during delivery.
- Smoking tobacco reduces the chances of IVF success and also increases the risk of miscarrying.
- Women who have dilated fallopian tubes do not have as much IVF success.
- Reducing the intake of caffeine and alcohol is thought to increase IVF success.
Winston, R 2006, A Child Against All Odds, Bantam Books, London.