Ovarian stimulation in IVF: what to expect
How ovarian stimulation fits into IVF
Ovarian stimulation is the part of an IVF cycle in which fertility medicines support the development of several follicles. The aim is not to produce as many eggs as possible at any cost. It is to find a response that gives the laboratory usable eggs while keeping your treatment as safe and manageable as possible.
The plan is individual. Age, medical history, ovarian reserve, previous treatment and the way your ovaries respond all matter. The ESHRE ovarian stimulation guideline describes individualisation, effectiveness, safety and patient experience as part of protocol selection.
Why stimulation does not reduce your egg supply
In a natural cycle, a group of follicles begins to develop and usually one becomes dominant. The others stop developing. Stimulation medicines support more than one follicle from that group to continue growing in the same cycle. They do not create new eggs, and they are not understood to make the ovaries run out sooner.
That explanation can make the process feel less mysterious, but it does not replace an individual discussion. Your doctor will explain what your ovarian reserve tests and previous response mean for your plan.
Common ovarian stimulation protocols
There is no single best protocol for everyone. A protocol may be changed because of ovarian reserve, PCOS, endometriosis, previous response, timing needs or safety considerations.
GnRH antagonist protocol
Stimulation usually starts near the beginning of the cycle. A GnRH antagonist is added later to reduce the chance of premature ovulation. This approach is commonly considered when the team wants a shorter, flexible cycle or wants to manage the risk of an excessive response.
Long GnRH agonist protocol
This approach includes a suppression phase before stimulation. It may be considered when the team needs more control over cycle timing or in selected clinical situations. It is not automatically better or worse than an antagonist protocol.
Mild stimulation or modified natural-cycle IVF
Lower medication doses, or close monitoring of a naturally developing follicle, may be discussed in selected situations. The expected number of eggs is usually lower, so the potential advantages and limitations need to be weighed carefully.
| Protocol | What it does | When it may be discussed | Important limitation |
|---|---|---|---|
| GnRH antagonist | Stimulates follicle growth and helps prevent premature ovulation | A commonly used option, including when response and OHSS risk need careful management | Still requires monitoring and individual dose adjustments |
| Long GnRH agonist | Suppresses the natural cycle before stimulation | When cycle timing or a particular clinical history makes this useful | Usually involves a longer treatment schedule |
| Mild or modified natural cycle | Uses less medication or follows a naturally developing follicle | When a lower-medication approach is being considered | It may produce fewer eggs in that cycle |
The table is a guide, not a treatment recommendation. Ask what your team is trying to achieve with the proposed protocol and what would make them change it.
What happens during the stimulation timeline?
1. Baseline assessment
The team usually checks the ovaries with ultrasound at the start of the cycle. Blood tests may be added when the clinical picture calls for them.
2. Daily stimulation medicines
Gonadotrophins containing FSH, with or without LH activity, are given by subcutaneous injection. A nurse should demonstrate the injection and tell you how to store and use each medicine.
3. Monitoring and dose changes
Ultrasound scans and, when appropriate, blood tests show how the follicles are developing. The dose can be adjusted, and the timing of the next visit may change. This is why another person’s number of injections or scan visits is not a reliable template for you.
4. Trigger injection
When the team considers the follicle development ready, they give a trigger injection to support final egg maturation. The exact medicine and time matter: follow the written instructions and contact the clinic immediately if you are unsure about the timing.
5. Egg retrieval
Egg retrieval is scheduled within a planned window after the trigger, commonly about 34–36 hours later. Your clinic will give you the exact appointment time and preparation instructions. You can read more in the guide to egg retrieval.
What might you feel?
Mild bloating, pelvic pressure, breast tenderness, tiredness, headache, mood changes or a small injection-site reaction can occur. Symptoms often become more noticeable as the ovaries enlarge. Tell the clinic if a symptom is severe, worsening or worrying you; do not wait for the next routine scan if you feel unwell.
Gentle movement, regular meals, fluids and practical support can make the days easier. As the ovaries enlarge, ask your team before doing high-impact exercise, heavy lifting or activities involving repeated twisting.
OHSS: what it is and when to ask for help
Ovarian hyperstimulation syndrome (OHSS) is an excessive response to stimulation. The risk is not the same for everyone. Higher ovarian reserve markers, PCOS and an anticipated high oocyte yield are among the factors that can increase risk, so the ASRM OHSS prevention guideline recommends risk-aware, individualised planning.
Prevention may include adjusting the gonadotrophin dose, choosing an antagonist protocol, using a GnRH agonist trigger in selected patients, or freezing embryos for later transfer when clinically appropriate. These decisions depend on your response and are made by the treating team.
Contact the clinic promptly for rapidly increasing abdominal swelling or weight, severe or persistent pain, repeated vomiting, shortness of breath or noticeably reduced urine. If symptoms are severe or you cannot reach the clinic, seek urgent medical care.
Dr. Aksoy’s approach
The purpose of monitoring is to understand your response, not to chase a number. We explain what each scan or blood test is checking, adjust the plan when needed and discuss safety decisions with you as the cycle develops. Your final protocol and medication doses should always come from the clinician managing your treatment.
Frequently asked questions
Are the injections painful?
The small subcutaneous needles are often described as a brief pinch, but comfort varies. Your clinic should show you the technique and explain what to do if an injection site becomes increasingly painful, red or swollen.
How long does ovarian stimulation last?
The injection phase often lasts around one to two weeks, but the exact length depends on your ovarian response and the protocol. Monitoring visits help the team decide when to give the trigger injection.
Can I work and exercise during stimulation?
Many people continue their usual routine, but gentle activity such as walking is usually more comfortable as the ovaries enlarge. Avoid strenuous or high-impact exercise and follow your clinic’s specific advice.
Does stimulation use up my eggs faster?
No. The medicines do not create a new egg supply or make the ovaries run out sooner. They support a group of follicles that has already started developing in that cycle, rather than allowing only one follicle to become dominant.
When should I contact the clinic about OHSS symptoms?
Contact your clinic promptly for rapidly increasing abdominal swelling or weight, severe or persistent pain, repeated vomiting, shortness of breath or noticeably reduced urine. These symptoms need individual medical advice.
Continue reading
Important information
This page is for general education and does not replace a consultation, diagnosis or personalised treatment plan. IVF protocols, medicines, monitoring and timing vary between patients. Do not change a dose or injection time without speaking with your treating team.
Sources
- European Society of Human Reproduction and Embryology. Ovarian stimulation in IVF/ICSI guideline.
- American Society for Reproductive Medicine Practice Committee. Prevention of moderate and severe ovarian hyperstimulation syndrome: a guideline.
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