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Stimulation of Eggs
Ovarian stimulation is a medication protocol applied to the prospective mother in order to obtain multiple eggs during egg retrieval. In this way, both the number and quality of embryos to be transferred to the uterus increase. Ovarian stimulation, one of the most critical stages of IVF treatment, is carried out with a personalized protocol based on the woman’s individual characteristics [1].
The prospective mother whose ovaries are stimulated with medication is monitored regularly by ultrasound, and the maturation of the eggs is checked. Mature eggs are retrieved transvaginally under ultrasound guidance; they are then transferred to the laboratory, where the high-quality ones are selected [1, 2].
How Are the Ovaries Stimulated in IVF Treatment?
To stimulate the ovaries, a baseline ultrasound examination is performed on the 2nd or 3rd day of menstruation. The condition of the uterus and ovaries is analyzed, and blood estrogen hormone levels and the AMH value are evaluated [1]. Then, the following steps are followed:
- Protocol selection: A GnRH antagonist or long agonist protocol is chosen by taking into account the patient’s ovarian reserve and conditions such as PCOS [1].
- Medication administration: Ovarian stimulation is started with gonadotropin injections containing FSH. The dosage is determined individually.
- Monitoring: At specific intervals, ultrasound examinations and, when necessary, estrogen measurements are performed to monitor the number of follicles and their growth rates. The aim of treatment is to achieve as many follicles measuring 16–20 mm in diameter as possible.
- Trigger injection: When the follicles reach the target size, an hCG or GnRH agonist “trigger” shot is administered. Egg retrieval is performed 34–36 hours after this injection [1].
Ovarian stimulation lasts an average of 10–11 days; however, the treatment duration may vary depending on the prospective mother’s individual response.
Egg Retrieval in IVF Treatment
One of the critical factors evaluated during ultrasound monitoring of the prospective mother is the structure and thickness of the endometrial lining. Endometrial receptivity is of great importance for the success of embryo transfer [3]:
- If the endometrial thickness on the day of hCG is 6 mm or thinner, the chance of pregnancy decreases significantly.
- An endometrial thickness of more than 14 mm may also have a negative effect.
- The optimal endometrial thickness for the transfer day is considered to be within the range of 7–14 mm [3].
After egg retrieval, the IVF treatment proceeds to the embryo transfer stage. Through the ICSI procedure, the highest-quality sperm is injected into the egg; the resulting embryos are transferred to a special culture medium. When they reach the 7–8 cell stage or the blastocyst stage, healthy embryos are transferred to the prospective mother’s uterus [2].
For detailed information about ovulation monitoring, you can review our ovulation monitoring page.
Frequently Asked Questions (FAQ)
Are ovarian stimulation injections painful?
Most patients find the injections tolerable. Mild bruising or swelling may occur at the injection site; this is temporary. Some patients may experience abdominal bloating or a feeling of tightness during the stimulation period.
How many eggs are targeted?
The goal is to obtain 10–15 mature eggs. Too few eggs limit embryo selection, while too many eggs increase the risk of OHSS (ovarian hyperstimulation syndrome). For this reason, the medication dose is carefully determined according to the person’s ovarian reserve (AMH and AFC values).
Why is endometrial thickness important?
The endometrium is the layered structure where embryo implantation occurs. The optimal thickness on the day of transfer is between 7–14 mm. Since thicknesses below 6 mm or above 14 mm may negatively affect implantation success, a frozen embryo transfer may be planned when necessary.
What is the purpose of the trigger shot, and why is its timing critical?
The trigger shot (hCG or GnRH agonist) completes the final maturation of the mature eggs within the follicles. Egg retrieval must be performed exactly 34–36 hours after this injection. Retrieval performed too early or too late may result in immature or overmature eggs.
Is there a stimulation risk in patients with PCOS?
Yes. In patients with PCOS, the risk of OHSS is higher due to a high antral follicle count. In these patients, a GnRH antagonist protocol and GnRH agonist trigger are preferred, and when necessary, the risk is minimized with a freeze-all strategy.
References
- Showell, M. G., et al. (2023). In Vitro Fertilization. StatPearls — NCBI Bookshelf. NBK562266. (https://www.ncbi.nlm.nih.gov/books/NBK562266/)
- American Society for Reproductive Medicine (ASRM). In Vitro Fertilization Treatment Journey. ReproductiveFacts.org. (https://www.reproductivefacts.org/patient-journeys/in-vitro-fertilization-treatment/)
- Liu, K. E. & Hartman, M. (2019). Endometrial preparation for frozen-thawed embryo transfer. Fertility and Sterility, 112(5), 810–817. PubMed PMID: 31561889. (https://pubmed.ncbi.nlm.nih.gov/31561889/)
- Mouanness, M., et al. (2020). Cumulative Live-Birth Rates by Maternal Age after One or Multiple In Vitro Fertilization Cycles. PMC7139227. (https://pmc.ncbi.nlm.nih.gov/articles/PMC7139227/)