There are five steps in the IVF process:
1. Ovarian stimulation
At the start of an IVF cycle, your doctor gives you hormones to stimulate your ovaries so they produce multiple eggs, rather than the single egg that normally develops each month. Multiple eggs are needed because some eggs won't fertilise or develop normally.
Many doctors also prescribe a birth control pill for one or more weeks before beginning IVF. The pill helps to prevent your body from releasing hormones that could stimulate natural ovulation.
You may need several different medications over the course of IVF to stimulate the production of eggs, to help the eggs mature, to prevent them being released too soon, and to prepare the lining of your uterus so it’s ripe for embryo implantation.
The doctor will use ultrasound imaging and hormone tests to monitor the developing eggs. The goal is to have at least 2 egg follicles that are approximately 15 to 18 mm in size. In most cases, more than 2 eggs develop; in some women, more than 20 may develop! When some follicles have reached the right size, an injection of medication is given to help them mature. Your doctor then schedules egg retrieval for 34 to 36 hours after the injection.
Sometimes your IVF cycle needs to be cancelled before the next step for one of these reasons:
- there aren’t enough developing follicles
- ovulation occurs too soon
- too many egg follicles develop, creating a risk of ovarian hyperstimulation syndrome
If the cycle is cancelled, your doctor might recommend changing medications or their doses to promote a better response during future IVF cycles.
It’s possible to perform IVF without ovarian stimulation. This is known as ‘natural cycle IVF’ or ‘unstimulated IVF’. Usually, only one egg is retrieved. However, the vast majority of IVF cycles worldwide are performed with some type of ovarian stimulation.
2. Egg retrieval
Egg retrieval can be done in your doctor’s clinic, a private clinic or a hospital. You’ll probably be offered IV sedation which will make you feel sleepy and relaxed. It’ll reduce your awareness of the procedure and any associated discomfort.
(After you’ve had sedation, you’ll have to wait around until it’s worn off before you go home. You’ll also need someone to accompany you home, as you won’t be safe to drive or travel alone.)
Once you’re sedated, your doctor looks for the egg follicles in your ovaries using an ultrasound probe. After they’re located, they’ll insert a thin probe that sucks up the eggs. The procedure takes approximately 15 to 30 minutes, depending upon how many egg follicles are present.
Your eggs are immediately placed in a culture dish designed to maximise the likelihood of successful fertilisation. Your doctor selects the healthy-looking eggs to mix with your partner’s sperm to create embryos, although not all eggs will be successfully fertilised.
3. Sperm retrieval
Your partner will be asked to attend the fertility clinic at the same time as the egg retrieval and provide semen (by masturbation) on the day of the egg retrieval. Other methods, such as testicular aspiration — the use of a needle or surgical procedure to extract sperm directly from the testicle — are sometimes required. Donor sperm can also be used if your partner’s sperm isn’t available or suitable.
The sperm are separated from the semen fluid in the lab, ready for combining with your eggs.
There are two common methods of fertilisation:
- Standard insemination (in vitro fertilisation or IVF). If sperm are normal, approximately 50,000 to 100,000 sperm are transferred to the dish containing the eggs. They’re mixed and incubated overnight.
- Intracytoplasmic sperm injection (ICSI). A single healthy sperm is injected directly into each mature egg under a high-powered microscope. If the sperm aren’t normal, or if previous IVF attempts have failed, this method may be used. It’s also used if the sperm have been surgically retrieved via testicular aspiration.
The fertilised eggs are assessed on the second and third day after retrieval. Embryos with good growth and development may be selected to grow to the next stage (blastocyst stage). Embryos at blastocyst stage are more likely to implant successfully.
In certain situations, your doctor may recommend other procedures before embryo transfer, such as:
- Assisted hatching. About 5 to 6 days after fertilisation, an embryo ‘hatches’ from its surrounding membrane, allowing it to implant into the lining of your uterus. If you're an older woman, or if you’ve have had multiple failed IVF attempts, your doctor might recommend assisted hatching — a technique in which a hole is made in the membrane around the embryo to help it to hatch and implant.
- Preimplantation genetic testing. Your doctor will recommend this if you’re having IVF to avoid passing on an inherited genetic disease, or transferring a chromosomally abnormal embryo. Your embryos will be developed until they reach a stage where a small sample of cells can be removed and tested, typically 5 to 6 days after fertilisation. Your doctor selects embryos that don't contain affected genes or chromosomes and transfers these ones to your uterus.
5. Embryo transfer
Embryo transfer is done in your doctor’s clinic, laboratory, a private clinic or hospital. Approximately 2 to 5 days after the egg retrieval, one or more eggs that have been fertilised (embryos) are placed into your uterus using a thin, flexible catheter inserted through your cervix. A syringe containing one or more embryos is attached to the end of the catheter so your doctor can place the embryo(s) into your uterus via your cervix. You probably won’t need sedation for this procedure, as there’s little or no discomfort.
Following the transfer, you may be encouraged to rest at home for several hours. Although studies don’t show that rest increases the chance of pregnancy, many women prefer not to resume their normal activities immediately.
Doctors normally recommend transferring a single embryo but it depends on your previous history of pregnancy and miscarriage, your age, and the quality of the embryos.
Younger women (under age 35) in their first cycle of IVF are often encouraged to have only one or two embryos transferred. If multiple attempts of IVF aren’t successful, your doctor may recommend transferring more embryos to increase your chances of pregnancy. With pre-implantation genetic testing and improved embryo selection techniques, higher pregnancy rates can be achieved with single embryo transfers. This reduces the need for transferring multiple embryos with the associated risks.
Embryos that aren’t transferred may be stored by freezing them (called cryopreservation). The chances of a successful pregnancy using a frozen embryo are the same as with a fresh transfer.