# IVF and ICSI > What IVF and ICSI are, who they are generally used for, the stages of a cycle, single embryo transfer, and their risks and limits, based on current guidelines. Source: https://www.ghinashami.com/en/interests/ivf-icsi/ Updated: 2026-10-13 Step 3 of 4 · Assisted reproduction In vitro fertilisation (IVF) means collecting eggs from the ovaries, fertilising them with sperm in the laboratory and transferring an embryo to the uterus. In ICSI, a single sperm is injected into each egg. This page explains the stages, who they are generally used for, and their risks. - 5 min read - Reviewed 13 October 2026 - 6 references ## Who IVF is generally used for - Blocked or damaged fallopian tubes - Sperm problems; when the sperm count is very low or the sperm move poorly, **ICSI** (injecting a single sperm into each egg) is used - Ovulation problems that have not responded to simpler treatment - Endometriosis, when other options have not worked or are not suitable - Unexplained infertility, either directly or after IUI has not worked - Older age, when female fertility is declining - Couples who need embryos tested for a known inherited condition ([PGT-M](https://www.ghinashami.com/en/interests/pgt-m/)) NICE advises ICSI when the semen analysis is abnormal, when fertilisation failed or was very low in a previous IVF cycle, and when sperm have been surgically retrieved. It advises against ICSI when the semen is normal and the cause of infertility lies elsewhere, because it has not been shown to help in that situation. ## The cycle, step by step Before the cycleAssessment and planning About 2 weeksStimulation Trigger, then collectionEgg collection 2 to 6 daysThe laboratory Fresh or frozenEmbryo transfer About 2 weeksThe wait About four to six weeks from the start of the injections to the pregnancy test. 1. Before the cycle Assessment and planning The fertility assessment, age and history guide the choice of medicines and protocol. Some protocols begin with medicines that switch off the natural cycle for two to three weeks; others do not. What to do in the months before is in the [preparing for IVF](https://www.ghinashami.com/en/guide/preparing-for-ivf/) guide. 2. About 2 weeks Stimulation Daily hormone injections encourage several follicles to grow at once. Ultrasound scans, and sometimes blood tests, check the response so that the dose can be adjusted and the risk of ovarian hyperstimulation kept down. 3. Trigger, then collection Egg collection A final injection matures the eggs, and the collection is timed after it. The eggs are collected with a needle passed through the vagina, usually under sedation; the procedure takes around 20 to 30 minutes. A sperm sample is prepared on the same day. 4. 2 to 6 days The laboratory Eggs are fertilised by conventional IVF, in which eggs and sperm are placed together, or by ICSI. Embryos are cultured for two to six days, often to the blastocyst stage. If embryo testing is planned ([PGT-M](https://www.ghinashami.com/en/interests/pgt-m/), or [PGT-A](https://www.ghinashami.com/en/interests/pgt-a/), whose benefit is debated), a few cells are taken from each embryo, and the embryos are frozen while the laboratory reports. 5. Fresh or frozen Embryo transfer An embryo is placed in the uterus through a thin tube passed through the cervix, guided by ultrasound. Guidelines favour transferring a single embryo, particularly for women under 37 in their first full cycle and whenever a top-quality blastocyst is available, because twins carry higher risks. Remaining good-quality embryos can be frozen for later use. When the risk of ovarian hyperstimulation is high, all embryos may be frozen and transferred in a later cycle. 6. About 2 weeks The wait You are given a date for a pregnancy test, usually around two weeks after the transfer. What those days are like, and what follows a positive test, is in [after your embryo transfer](https://www.ghinashami.com/en/guide/after-embryo-transfer/). ## What the guidelines recommend 1. 1 One embryo at a time NICE advises a single embryo transfer for women under 37 in their first full cycle and whenever a top-quality blastocyst is available, and never more than two embryos in any cycle, because twins and triplets carry serious risks for mothers and babies. 2. 2 ICSI only when it is needed ICSI is advised for sperm problems, after previous failed fertilisation and with surgically retrieved sperm; it has not been shown to help when the semen is normal. 3. 3 Caution with add-ons NICE advises against several extras sometimes added to IVF, including endometrial scratching, routine hysteroscopy, endometrial receptivity testing, immune treatments, assisted hatching and PGT-A to improve live birth rates. 4. 4 Support throughout Counselling is recommended for anyone having IVF, before treatment, during it and after it, whatever the outcome. Dr. Ghina Shami ## Risks and limits **Ovarian hyperstimulation syndrome (OHSS).** The ovaries can over-respond to the stimulation medicines and become enlarged and painful. Mild OHSS is fairly common; severe OHSS is rare but can be life-threatening. The risk is assessed before stimulation and can be lowered, for example by using a different trigger injection and freezing all embryos. **Multiple pregnancy.** Transferring more than one embryo increases the chance of twins or triplets, which can seriously affect the health of the mother and the babies. **Egg collection.** Infection, bleeding and, rarely, injury to the bowel can follow the procedure. **Pregnancy.** The risk of ectopic pregnancy is higher than in the general population. IVF pregnancies have slightly higher rates of complications such as pre-eclampsia, gestational diabetes and high blood pressure, and some studies suggest a small increase in birth defects, although the overall risk for each person remains low. **Medicines and the long term.** The hormone medicines can cause side effects. NICE advises that the absolute long-term risks for women and for children born after IVF are low, although a small increase in the risk of borderline ovarian tumours cannot be excluded. **Limits and emotional load.** A cycle may not lead to a pregnancy, and the chance varies widely with age, ovarian reserve and the reason for treatment. IVF can be emotionally and physically demanding. ## Common questions **What is the difference between IVF and ICSI?** In conventional IVF, eggs and sperm are placed together in a dish and fertilisation happens on its own. In ICSI, an embryologist injects a single sperm into each egg. ICSI is used for sperm problems, after fertilisation has failed in a previous cycle and with surgically retrieved sperm; guidelines advise against it when the semen is normal. **Should embryos be tested with PGT-A?** NICE advises against PGT-A as part of fertility treatment to improve live birth rates, and the HFEA rates it red for improving the chance of having a baby for most patients, while rating it green for reducing the chance of miscarriage. The [PGT-A](https://www.ghinashami.com/en/interests/pgt-a/) page explains the evidence; your doctor can advise whether it has any role in your situation. **Fresh or frozen transfer?** It depends on the response to stimulation, the risk of ovarian hyperstimulation and whether embryos are being tested. When the risk of OHSS is high, guidelines recommend freezing all embryos and transferring one in a later cycle. For women with regular cycles, NICE notes that the chance of a live birth from a frozen embryo is similar whether it is transferred in a natural cycle or a hormone-supported one. Your doctor can advise on the choice. **How long does an IVF cycle take?** For most people, a cycle takes four to six weeks from the start of the medicines to the pregnancy test. With embryo testing or a frozen transfer, add the time for the laboratory report and for the transfer cycle. **Evidence basis:** This page is based on international clinical guidelines (NICE 2026, ESHRE 2025 update), on HFEA and NHS patient information and on the studies they cite; where the evidence is limited, the page says so. ## References 1. Fertility problems: assessment and treatment, NICE (guideline NG257) (2026) — [nice.org.uk](https://www.nice.org.uk/guidance/ng257) 2. ESHRE guideline: ovarian stimulation for IVF/ICSI: an update in 2025, ESHRE, Human Reproduction (2026) — [doi:10.1093/humrep/deag018](https://doi.org/10.1093/humrep/deag018) 3. In vitro fertilisation (IVF), HFEA (2016) — [hfea.gov.uk](https://www.hfea.gov.uk/treatments/explore-all-treatments/in-vitro-fertilisation-ivf/) 4. Intracytoplasmic sperm injection (ICSI), HFEA (2016) — [hfea.gov.uk](https://www.hfea.gov.uk/treatments/explore-all-treatments/intracytoplasmic-sperm-injection-icsi/) 5. Risks of fertility treatment, HFEA (2016) — [hfea.gov.uk](https://www.hfea.gov.uk/treatments/explore-all-treatments/risks-of-fertility-treatment/) 6. IVF, NHS (2025) — [nhs.uk](https://www.nhs.uk/tests-and-treatments/ivf/) Written and reviewed by [Dr. Ghina Shami](https://www.ghinashami.com/en/about/), Consultant, Reproductive Medicine and Infertility · 13 October 2026 · [How these pages are prepared](https://www.ghinashami.com/en/legal/#accuracy)