IVF Explained: How In Vitro Fertilisation Works, Step by Step
Key takeaways
- IVF means combining an egg and sperm in a laboratory, then transferring a resulting embryo to the womb; one full cycle usually takes about four to six weeks.
- A cycle has clear stages: ovarian stimulation, egg collection, fertilisation in the lab, embryo development, and embryo transfer, followed by the two-week wait.
- Success falls with age and varies by clinic and cause, so it often takes more than one cycle; your own team can give you a personalised estimate.
- IVF is physically and emotionally demanding and can be costly; knowing the steps in advance makes it feel far more manageable.
IVF, in vitro fertilisation, means bringing an egg and sperm together in a laboratory and then placing a resulting embryo into the womb. Put like that it sounds simple; in practice it’s a series of clear stages over about four to six weeks. Knowing those stages in advance was the single thing that made it feel manageable for me. This is the main guide.
The stages of an IVF cycle
1. Ovarian stimulation
You take hormone medication (usually daily injections) for around two weeks to encourage your ovaries to produce several mature eggs rather than the single egg of a normal cycle. You’re monitored with scans and blood tests along the way.
2. Egg collection
When the eggs are ready, they’re collected in a short procedure under sedation, using a fine needle guided by ultrasound. It usually takes about 20 to 30 minutes, and you go home the same day.
3. Fertilisation in the lab
The eggs are combined with sperm in the laboratory, either by mixing them together or by injecting a single sperm into each egg (ICSI). The lab then watches to see how many fertilise.
4. Embryo development
The fertilised eggs grow for a few days under careful conditions. The embryologist assesses them and chooses the most suitable for transfer.
5. Embryo transfer
One embryo (usually) is placed into the womb through a thin catheter, a quick procedure that doesn’t need sedation. Any other good-quality embryos can often be frozen for future attempts.
6. The two-week wait
About two weeks later, a pregnancy test tells you whether the cycle has worked. This wait is, for many people, the hardest part emotionally, see our guide to coping with the emotional side.
How well does it work?
Success depends heavily on age and the cause of infertility, and it varies between clinics, which is why it often takes more than one cycle. We cover this in detail in IVF success rates.
Risks and things to know
IVF is generally safe but has risks, including ovarian hyperstimulation syndrome (OHSS), a higher chance of multiple pregnancy if more than one embryo is transferred, and the emotional and financial toll of treatment. Your clinic will talk these through with you.
This guide is general information, not a diagnosis or treatment plan. Your own fertility team can advise on the right approach for you.
References
- IVF, NHS.
- What is IVF?, Human Fertilisation and Embryology Authority (HFEA).
- In Vitro Fertilization (IVF), American Society for Reproductive Medicine (ReproductiveFacts.org).
Frequently asked questions
How does IVF work?
IVF (in vitro fertilisation) involves stimulating the ovaries to produce several eggs, collecting them in a short procedure, combining them with sperm in a laboratory to create embryos, letting those embryos develop for a few days, and then transferring one to the womb. Any suitable remaining embryos can often be frozen for later. About two weeks after transfer, a pregnancy test shows whether it has worked.
How long does one cycle of IVF take?
A single full cycle typically takes about four to six weeks from the start of ovarian stimulation to the pregnancy test, though this varies with the protocol your clinic uses and whether you have a fresh or frozen embryo transfer. Preparation and tests beforehand can add more time.
How many rounds of IVF does it usually take?
There's no fixed number; many people need more than one cycle, and success depends heavily on age and the cause of infertility. Some conceive on the first cycle, others need several. Your fertility team can give you a more personal estimate based on your situation and clinic results.
Is IVF painful?
Most of IVF is uncomfortable rather than painful. The daily stimulation injections use very fine needles and sting briefly; egg collection is done under sedation so you do not feel it, though some cramping and bloating afterward are common; and embryo transfer is usually painless, much like a smear test. Tell your clinic about any pain, as they can help.
What is the difference between IVF and ICSI?
In standard IVF, eggs and sperm are mixed together in a dish and fertilisation happens on its own. In ICSI, an embryologist injects a single sperm directly into each egg, which is mainly used when there is a sperm problem. The rest of the cycle is the same, and your clinic will advise which suits you.
Written by Emma Lawson. Medically reviewed by Dr Priya Nair, MBBS, MRCOG.
Our guides are written from personal experience and reviewed by a qualified clinician for accuracy. Read our editorial policy.