What happens in IVF?

Different combinations of fertility drugs can be used in IVF. Your doctor should explain the benefits, risks and side effects of each treatment and assess your risks individually before deciding which drugs to offer you.

Pre-treatment

You may be offered the oral contraceptive pill or progestogen tablets before IVF. This makes it easier to time when you need to start taking fertility drugs (because your doctor will know when your period is due). Taking the pill in this way does not mean you are less likely to have a baby.

Step 1: down-regulation of the ovaries

Depending on the type of treatment you are having, you may be offered drugs called gonadotrophin-releasing hormone agonists to 'switch off' egg production in your ovaries. These drugs make the ovaries more receptive to the gonadotrophins which are used later on to stimulate the ovaries into producing eggs. Down‑regulation is not the only method used to control your cycle in IVF. Your doctor should explain which option would be most suitable for you.

Step 2: ovarian stimulation

Ovarian stimulation involves taking hormones to help your ovaries produce more than 1 egg at a time (unlike your natural cycle). You should be offered IVF with ovarian stimulation, as this gives you a better chance of pregnancy than IVF using your natural cycle (where 1 egg is collected during your normal menstrual cycle without the use of hormones). You should not be offered 'natural-cycle IVF'.

Gonadotrophins are used to stimulate the ovaries to produce extra eggs in IVF. These are the same drugs that may be used to help produce eggs if you do not ovulate normally.

You should be offered a hormone called human chorionic gonadotrophin (hCG) to help your eggs mature so they are ready to be collected. You should be offered monitoring by ultrasound throughout your ovarian stimulation to check how your ovaries are responding and to check for signs of ovarian hyperstimulation syndrome.

Step 3: egg collection

Your eggs should be collected through a needle, guided through your vagina by ultrasound. You should be given an injection to relieve any pain and to make you sleepy during this procedure.

Step 4: obtaining sperm

Men should usually be asked to produce a sperm sample if possible on the same day as the woman's eggs are collected.

If you have a condition (such as a spinal cord injury) that prevents you from ejaculating, there are treatments that may help you. Otherwise you may be offered surgical sperm recovery.

If your sperm count is low or the sperm are poor‑quality, you and your partner may be offered further procedures as well as IVF. They are intracytoplasmic sperm injection and donor insemination.

Step 5: fertilisation of the eggs

Once eggs and sperm have been collected, they are mixed together and placed in an incubator. The sperm may then fertilise some of the eggs. Any resulting embryos are kept in the incubator for up to 6 days before they are placed into the woman's womb.

Step 6: transfer of embryos

Placing more than 1 embryo in your womb increases your chances of becoming pregnant but it also increases the risk of multiple pregnancy. Your doctor should make sure you are aware of this risk. You should not have more than 2 embryos transferred at one time.

The decision to transfer 1 or 2 embryos is based on your age, the quality of the embryos, and whether you have had unsuccessful IVF cycles previously. Younger women usually have better‑quality embryos. This improves the chances of pregnancy. If you are using donor eggs it should be the donor's age rather than your age that is used to help judge embryo quality.

The table below gives a guide to how many embryos you should have transferred, based on your (or your egg‑donor's) age.

How many embryos should be transferred?

Your age

Treatment cycle

First full cycle

Second full cycle

Third full cycle

Under 37 years

1 embryo

1 embryo if a top‑quality one is available; otherwise 2 embryos may be considered

No more than 2 embryos

37–39 years

1 embryo if a top‑quality one is available; otherwise 2 embryos may be considered

1 embryo if a top‑quality one is available; otherwise 2 embryos may be considered

No more than 2 embryos

40–42 years

2 embryos may be considered

The doctor should use ultrasound to guide the placement of the embryo into your womb. You do not need to stay in bed for long after the embryo transfer as this has not been shown to make any difference to the chance of pregnancy.

After IVF you should be offered progesterone to help the embryo to attach inside the womb. If you become pregnant, you do not need to take progesterone for longer than 8 weeks after conception.

Freezing embryos after IVF

After your embryo transfer, if there are any remaining good‑quality embryos, you should be offered the chance to freeze them for possible use later.

An embryo that has been frozen can be thawed and transferred into your womb either as part of your natural cycle or as part of a cycle controlled by hormone treatment. If you ovulate regularly, your chances of a successful pregnancy after thawed embryo transfer are similar whether your cycle is natural or stimulated.

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