In vitro fertilization (IVF) is a treatment in which an egg is fertilized by sperm in the laboratory, and the resulting embryo is then placed in the uterus. This article follows a cycle step by step, explains who it is for and what the main risks are. For a general overview of infertility and other techniques, see our article on medically assisted procreation; for the variant in which a single sperm is injected into the egg, see our article on ICSI.
What is IVF and who is it for?
The NHS describes IVF as a treatment in which eggs are fertilized with sperm in a laboratory and the resulting embryo is placed in the womb. It is generally considered when other treatments have not worked.
French medical teaching lists the main indications for conventional IVF:
- damaged or blocked fallopian tubes;
- moderate sperm abnormalities;
- unexplained infertility, first-line or after failed ovulation induction or insemination;
- endometriosis;
- ovulation disorders after failed simpler treatments;
- reduced ovarian reserve that is still sufficient;
- failed insemination with donor sperm.
Severe sperm abnormalities are usually treated with ICSI rather than conventional IVF.
Step 1: ovarian stimulation and monitoring
The aim is to obtain several mature eggs rather than the single one of a natural cycle. According to the NHS, a full IVF cycle takes about 3 to 6 weeks. Depending on the protocol, a first phase of 2 to 3 weeks may suppress natural egg production, followed by daily hormone injections for about 2 weeks.
Progress is followed by ultrasound and hormone tests. The Revue du Praticien explains that the trigger injection is given once most follicles reach about 18 mm. Protocols vary, so the exact duration is set by your medical team.
Step 2: egg retrieval and sperm collection
Eggs are collected by ultrasound-guided aspiration through the vagina, 34 to 38 hours after the trigger injection. The NHS states that the procedure takes about 20 minutes and that a sedative is offered. The sperm sample is usually provided on the same day; donor sperm, if used, is prepared in the laboratory. In France, the Agence de la biomédecine specifies that retrieval is done under analgesia, local anesthesia or general anesthesia.
Step 3: fertilization and embryo culture
In conventional IVF, each egg is incubated with a prepared sperm sample. The next day, the laboratory checks which eggs are fertilized (two pronuclei visible); the clinic then reports the number of embryos. The embryos develop in culture, and transfer takes place on day 2 or 3, or at the blastocyst stage (day 5 to 6).
Several eggs can be fertilized in the same cycle, but not all become usable embryos. If the sperm quality does not allow classical fertilization, the laboratory may use ICSI, described in our dedicated article.
Step 4: embryo transfer, freezing and what if it fails
The embryo is placed in the uterus with a thin tube passed through the vagina. One or two embryos are transferred, with single-embryo transfer preferred, and progesterone supports the uterine lining. Good-quality surplus embryos can be vitrified (frozen). A pregnancy test follows about two weeks later: the NHS gives a date around 16 days after the transfer.
If the attempt fails, the situation is not simply a matter of repeating the last step. If frozen embryos from the same cycle remain, a later frozen embryo transfer can be done without new stimulation or egg retrieval. If none remain, a new cycle starting from stimulation is needed. Your specialist will adjust the protocol after reviewing the cycle. In France, the Agence de la biomédecine adds that the patients are consulted in writing each year on the fate of stored embryos.
What are the risks and the results?
The main risks are:
- Ovarian hyperstimulation syndrome (OHSS): the HFEA reports that around a third of women develop a mild form, usually treated at home; severe symptoms typically appear the week after egg collection and need urgent care.
- Multiple pregnancy: the HFEA notes that at least half of twins are born premature and underweight, which is why the aim is a low multiple birth rate.
- Ectopic pregnancy and, rarely, infection or bleeding after procedures.
Results depend on age, the cause of infertility, BMI and lifestyle, according to the NHS. In France in 2023, live births followed 18.7% of conventional IVF attempts with the couple’s own gametes, and 25.8% of embryo transfers. These national averages cannot predict an individual outcome.
When should you discuss IVF with your doctor?
Discuss IVF with a fertility specialist if you have not conceived after a year of trying (sooner if the woman is 36 or over, or if a cause is already known), or if a simpler treatment has not worked. Before starting, ask about:
- the assessment of both partners and the reason IVF is proposed;
- the stimulation protocol and how side effects are monitored;
- how many embryos will be transferred and what happens to those that are frozen;
- the signs that require urgent contact with the clinic after egg collection.
Further reading at La Rose Clinic
Frequently asked questions
How long does an IVF cycle last?
According to the NHS, a full cycle takes about 3 to 6 weeks, depending on the protocol; stimulation itself lasts about 2 weeks.
Is egg retrieval painful?
It takes about 20 minutes and a sedative is offered, according to the NHS. Anesthesia options are discussed with your team beforehand.
What happens to the embryos that are not transferred?
Good-quality surplus embryos can be frozen for a later transfer, without a new stimulation. Their future is decided with the clinic and reviewed regularly.
What is the risk of twins?
Transferring more than one embryo raises the chance of a multiple pregnancy, which carries more risks for mother and babies. Single-embryo transfer is preferred in France.
References
- IVF (nhs.uk)
- What happens during IVF (nhs.uk)
- Risks of fertility treatment (hfea.gov.uk)
- Assistance médicale à la procréation : aspects biologiques, médicaux et éthiques (larevuedupraticien.fr)
- L’assistance médicale à la procréation (guide) (agence-biomedecine.fr)
- Rapport médical et scientifique : AMP 2023 (rams.agence-biomedecine.fr)
This article is for information only. It does not replace a medical consultation: if in doubt, talk to your doctor.
