Low ovarian response is a situation that can occur during assisted reproduction treatment, particularly during in vitro fertilization (IVF-ICSI). It happens when the ovaries respond less than expected to hormonal stimulation, resulting in a reduced number of follicles or oocytes.
For many patients, being told that they have a "low response" can be worrying. However, it does not always mean that treatment has come to an end or that there are no alternatives. The important thing is to understand what has happened, which factors may be influencing the outcome, and which strategy makes the most sense in each individual case.
Low ovarian response and low ovarian reserve: are they the same thing?
Although they are related, they do not mean exactly the same thing. Ovarian reserve refers to the number of eggs available in the ovaries at a given point in time. Low ovarian response, on the other hand, describes how the ovaries respond when stimulated during treatment.
A woman may have a low ovarian reserve and therefore be at greater risk of producing a small number of oocytes. It can also happen that the response is lower than expected despite having acceptable markers.
Tests such as anti-Müllerian hormone (AMH), antral follicle count by ultrasound, and, in some cases, other hormone tests are used to assess ovarian reserve. ASRM notes that these tests help predict the response to stimulation, although they do not determine the chances of pregnancy on their own.
Why can low ovarian response occur?
The most common cause is a decline in ovarian reserve, which is usually associated with age. As the years go by, the number of available eggs decreases, and their quality may also be affected.
In addition to age, other factors may play a role:
- A history of ovarian surgery.
- Endometriosis.
- Medical treatments such as chemotherapy.
- Genetic or autoimmune alterations.
- An individual low response to medication.
- Previous cycles in which few oocytes were retrieved.
In some cases, a low response is suspected before treatment begins. In others, it is detected during stimulation or after egg retrieval.
What is assessed after detecting a low response?
Before deciding on the next step, it is advisable to review the entire cycle. It is not enough to look at how many eggs were obtained. It is also important to analyze how many follicles were present at the beginning, how they developed, what medication was used, how many oocytes were mature, whether they were fertilized correctly, and how the embryos developed.
This information makes it possible to distinguish between different situations. Obtaining a small number of mature eggs with good embryo development is not the same as retrieving many immature oocytes or embryos that stop developing during the first few days. Each detail can help guide the subsequent strategy.
Options when there is low ovarian response
One of the first possibilities is to adjust the stimulation protocol. The dose, type of medication, timing of initiation, or combination of drugs may be adjusted. The goal is to make the best possible use of the follicles available in that particular cycle.
In patients with low ovarian response, substantially increasing the medication does not always result in more oocytes. For this reason, the ESHRE guidelines on ovarian stimulation emphasize tailoring the strategy to the individual and assessing each case according to the patient's clinical profile.
Another option may be oocyte accumulation, a technique that allows the oocytes obtained over several cycles to be vitrified and used later. Embryo accumulation may also be considered, by fertilizing the oocytes from each cycle and vitrifying the resulting embryos.
It is also important to take the male factor into account. When only a small number of oocytes are available, each one counts, so it is worth assessing whether sperm quality, fertilization, or embryo development may be influencing the outcome.
When should other alternatives be considered?
If the ovarian response is very low, if several cycles fail to produce viable embryos, or if the prognosis with one's own eggs is limited, egg donation may be considered. It does not necessarily have to be the first option, but it may become part of the discussion when the chances of success with one's own oocytes are very low.
For women who are not yet trying to become pregnant but have a low ovarian reserve, fertility preservation may be an option to consider as soon as possible, particularly if they wish to postpone motherhood.