What Is IVF and How Does It Work?
In vitro fertilisation (IVF) is a medical procedure in which mature eggs collected from the ovaries are fertilised by sperm in an embryology laboratory. The resulting embryos are cultured for several days before a selected embryo, or in some circumstances more than one, is transferred into the uterus according to the clinical plan and applicable regulations.
Below, Dr. Senai Aksoy walks through the six clinical and laboratory steps in an animated explainer. The written guide that follows details each phase, explains when microinjection (ICSI) is needed, and outlines how treatment is organised for international patients in Istanbul.
The Six Core Stages of IVF Treatment
An IVF cycle progresses through six sequential phases. While the general roadmap is consistent, individual timelines vary depending on whether you undergo a fresh embryo transfer or a freeze-all protocol.
| Step | Stage Name | Primary Clinical Action | Typical Timing |
|---|---|---|---|
| 1 | Consultation & Diagnostic Workup | Medical history, AMH/antral follicle count, semen analysis, pelvic ultrasound | Days/weeks before cycle |
| 2 | Controlled Ovarian Stimulation | Daily gonadotropin injections to develop multiple mature follicles; ultrasound and estradiol monitoring | 9–12 days |
| 3 | Egg Retrieval (Oocyte Pick-Up) | Transvaginal ultrasound-guided aspiration under light intravenous sedation | ~35–36 hours post-trigger |
| 4 | Laboratory Fertilisation & Culture | Insemination (conventional IVF) or microinjection (ICSI); culture to a day-3 cleavage-stage embryo or a day-5/6 blastocyst | 3–6 days in laboratory |
| 5 | Embryo Transfer | Ultrasound-guided placement of 1 (or 2) selected embryos into the uterine cavity | Day 3 or Day 5 after retrieval |
| 6 | The Two-Week Wait & Beta-hCG Test | Luteal phase progesterone support followed by a quantitative blood pregnancy test | 10–14 days post-transfer |
1. Diagnostic Evaluation and Protocol Selection
Before initiating hormone therapy, an individual assessment helps determine whether IVF is indicated and which medication protocol may offer an appropriate and safe response. Pre-treatment investigations may include:
- Ovarian reserve testing: Serum anti-Müllerian hormone (AMH) and transvaginal antral follicle count (AFC) to estimate follicular recruitment potential.
- Semen analysis: Evaluating sperm count, motility, and morphology to determine whether conventional IVF or ICSI is appropriate.
- Uterine cavity assessment: Pelvic ultrasound, saline-infusion sonography, or hysteroscopy to rule out polyps, submucosal fibroids, or intrauterine adhesions.
Explore the complete diagnostic checklist in our guide to pre-IVF testing.
2. Controlled Ovarian Stimulation
In a natural cycle, a woman typically ovulates a single egg. In IVF, injectable follicle-stimulating hormone (FSH) and luteinizing hormone (LH) analogues recruit multiple follicles simultaneously.
During this period, which often lasts 9 to 12 days, ultrasound scans and, when indicated, blood tests are used to monitor follicular growth. Gonadotropin doses are adjusted to balance ovarian response with safety, including the risk of ovarian hyperstimulation syndrome (OHSS), in line with the ESHRE ovarian stimulation guideline. The timing and type of trigger injection are then selected according to the follicular response and treatment plan.
Learn more about medication protocols in our guide to ovarian stimulation.
3. Egg Retrieval (Oocyte Pick-up)
Egg retrieval takes place 35 to 36 hours after the trigger shot. Under light intravenous sedation (conscious sedation or monitored anaesthesia care), the reproductive specialist inserts a fine aspiration needle guided by transvaginal ultrasound into each ovarian follicle.
The follicular fluid is immediately passed to the adjacent embryology laboratory, where embryologists identify and isolate mature oocytes. The procedure lasts 15 to 25 minutes, and patients generally rest in the recovery suite for 1 to 2 hours before returning to their hotel or home.
Read what to expect before and after the procedure in our guide to egg retrieval.
4. Laboratory Fertilisation: IVF vs ICSI
On the day of retrieval, the partner provides a fresh semen sample (or frozen sperm is thawed). The embryology team washes and prepares the sperm to select the most motile, morphologically normal spermatozoa.
Fertilisation is achieved via one of two established methods:
- Conventional IVF: Eggs and prepared sperm are placed together in a culture dish, allowing natural penetration and fertilisation.
- Intracytoplasmic Sperm Injection (ICSI): An embryologist immobilises a single spermatozoon and injects it directly into the cytoplasm of each mature metaphase-II oocyte under high-magnification microscopy.
The fertilised eggs (zygotes) are cultured in specialised incubators to day 3 (cleavage stage) or day 5/6 (blastocyst stage), depending on embryo development and the treatment plan. Detailed laboratory comparisons are available in our guide to fertilisation — IVF and ICSI.
5. Embryo Transfer and Cryopreservation
Embryo transfer is generally brief and is usually performed without anaesthesia. Under transabdominal ultrasound guidance, the physician passes a soft, flexible catheter through the cervix and places the selected embryo in the uterine cavity.
Additional embryos that meet the laboratory’s criteria for cryopreservation may be vitrified and stored in liquid nitrogen for a future frozen embryo transfer (FET). This can allow another transfer without repeating ovarian stimulation and egg retrieval.
Learn about transfer preparation in our guide to embryo transfer and preservation in our overview of embryo freezing.
6. The Two-Week Wait and Pregnancy Testing
Following embryo transfer, progesterone may be prescribed to support the luteal phase and endometrial lining.
Approximately 10 to 14 days after transfer, a quantitative serum beta-hCG test measures the pregnancy hormone level. If the result is positive, the clinical team may repeat the test to assess the pattern of change and arrange an ultrasound at the appropriate gestational age.
To understand pregnancy hormone ranges, read our clinical guide to beta-hCG test results after IVF.
Conventional IVF versus ICSI: How the Decision Is Made
Patients often ask whether ICSI is always “better” than conventional IVF. Scientifically and clinically, both techniques have distinct indications:
- Conventional IVF allows prepared sperm to fertilise the oocyte in the culture dish. It is an appropriate option when there is no clear indication for ICSI, including when semen parameters are within the expected range.
- ICSI can overcome severe sperm-related barriers, such as a very low count, poor motility or the use of surgically retrieved sperm. It may also be considered when conventional insemination previously resulted in lower-than-expected or failed fertilisation.
According to the 2026 committee opinion from the American Society for Reproductive Medicine (ASRM) and Cochrane systematic reviews, routine ICSI in non-male-factor cases does not improve clinical pregnancy or live-birth rates compared with conventional IVF.
Laboratory Quality and Electronic Witnessing Systems
In assisted reproduction, patient safety and sample integrity are central laboratory priorities. Embryology laboratories use controlled systems for air quality, temperature and gas conditions in accordance with their applicable quality standards.
To reduce the risk of sample mix-ups during gamete handling and embryo culture, some centres employ electronic witnessing systems such as RFID or barcode tracking. These systems can verify culture dishes, tubes and patient identifiers at defined points in the laboratory process; they complement, rather than replace, trained staff and other identity checks.
Single Embryo Transfer (SET) and Safety Regulations in Turkey
Under Turkish Ministry of Health regulations, assisted reproduction treatment in Türkiye is subject to specific eligibility and embryo-transfer rules:
- Single Embryo Transfer (SET): For women under the age of 35 in their first and second treatment cycles, transferring a single embryo is legally mandated to minimize maternal and fetal complications associated with twin and triplet pregnancies. Transferring a maximum of two embryos is permitted only after two unsuccessful cycles or in women aged 35 and older.
- Own-Gamete Treatment Only: Treatments in Turkey are exclusively available to legally married heterosexual couples using their own eggs and sperm. Donor eggs, donor sperm, donor embryos, and gestational surrogacy are strictly prohibited by law.
- No Non-Medical Sex Selection: Gender selection for family balancing is illegal; preimplantation genetic testing (PGT) is restricted to medical indications and severe sex-linked genetic disorders.
Planning IVF in Turkey as an International Patient
International couples considering treatment in Istanbul can plan their stay around the main clinical milestones:
- Remote Medical Assessment: Share previous fertility records, hormone results and semen analyses for specialist review before making travel arrangements.
- Travel Timeline: The length of stay depends on the protocol, response to stimulation and whether a fresh transfer is planned. Some patients may begin monitoring in their country of residence and travel to Istanbul later in the stimulation phase, provided the treating teams coordinate the plan.
- Itemised Estimate: Request a written estimate that distinguishes the clinical cycle from medication, ICSI when indicated, embryo culture, vitrification and any planned genetic testing.
For a full breakdown of travel logistics, visit our guides on IVF in Turkey for international patients, IVF treatment timeline, and IVF / ICSI treatment pricing.
Sources & Scientific References
- European Society of Human Reproduction and Embryology (ESHRE). Ovarian Stimulation for IVF/ICSI: Guideline. Updated 2025. ESHRE guideline
- Practice Committee of the American Society for Reproductive Medicine (ASRM). Intracytoplasmic sperm injection for nonmale factor indications: a committee opinion. Fertility and Sterility, 2026. ASRM committee opinion
- National Institute for Health and Care Excellence (NICE). Fertility problems: assessment and treatment (Clinical Guideline CG156). Updated 2017. NICE Guidelines
- Cochrane Gynaecology and Fertility Group. Intracytoplasmic sperm injection (ICSI) versus conventional techniques for oocyte insemination in IVF. Cochrane Database of Systematic Reviews, 2023. Cochrane Library
- Turkish Ministry of Health. Üremeye Yardımcı Tedavi Uygulamaları ve Üremeye Yardımcı Tedavi Merkezleri Hakkında Yönetmelik. Official regulation
- ESHRE IVF Laboratory Working Group. Revised guidelines for good practice in IVF laboratories. Human Reproduction, 2026. ESHRE recommendations
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