Virtually all in vitro fertilization (IVF) processes include an ovarian stimulation treatment. The objective of this is to favor the development of more than one ovarian follicle since only one would develop naturally, in order to obtain a greater number of mature eggs and increase the probability of pregnancy.
Faced with this treatment, many women ask themselves the following question: How many eggs must be obtained in order to achieve pregnancy in an IVF process? Although there is no single answer, there are certain important aspects related to this question.
Provided below is an index with the 7 points we are going to expand on in this article.
Ovarian response during IVF cycles
The ovarian response to the stimulation carried out in the IVF-ICSI cycles will vary from one woman to another depending on the indicated medication regimen, the woman's fertility situation, etc. Thus, we can distinguish three types of women based on their response to ovarian stimulation:
- Low responders: these are women from whom it has only been possible to obtain a maximum of 3 ovules in the follicular puncture after stimulation. In this group, we find women with a low ovarian reserve due to age, but also those women with certain pathologies that prevent obtaining a greater number of eggs.
- Normoresponders: in these women, after ovarian stimulation it is possible to obtain between 4-15 ovules per cycle. However, there are those who differentiate a subgroup called suboptimal response for patients from whom between 4-9 oocytes are obtained.
- Hyper-responders: this group corresponds to women from whom more than 15 oocytes per cycle can be obtained. They are usually young women without fertility problems, such as donors.
- Low responders
- When the number of eggs retrieved is 3 or less. Some clinics set this limit on 5 eggs. It typically corresponds to women with poor ovarian reserve due to age, as well as those with certain conditions that prevent the development of a higher amount of eggs.
- Normal responders
- Fortunately, most women can be included in this second group. It means that a good number of eggs is retrieved after undergoing stimulation. Broadly speaking, the average number of eggs is 6-7 or even 9-10 per cycle.
- High responders
- We include here cases where 20 or more eggs per cycle are obtained. The profile of these patients is typically associated with young girls, without fertility problems. A good example is egg donors. Even though it occurs rarely, there have been cases in which over 50 eggs have been retrieved.
It is very important that, during the period of ovarian stimulation, the woman goes to the specialist's office for an ultrasound and analytical controls. In this way, the gynecologist will be able to assess the response of the ovary to the hormonal medication administered and adjust the dose if necessary.
That a woman is in one group or another of ovarian response is not indicative of pathology. As an example, it is normal for a 45-year-old woman to be a low-responder. In fact, few eggs are obtained in the puncture because her ovarian reserve is low since she is close to menopause.
For its part, a healthy 20-year-old woman is expected to respond excessively to stimulation, so it will be essential to properly control the dose of medication. The most unusual thing, in this case, would be that this young woman manifested a low response.
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Estimation of the number of oocytes
Follicular puncture is the surgical intervention in which the ovules are obtained after ovarian stimulation. The objective of this procedure is to extract the ovules when they are in a stage of maturation known as metaphase II. This is the stage considered mature since it is in which the fertilization of the oocyte by the sperm can occur.
To schedule the follicular puncture at the right time and to be able to predict, approximately, the number of ovules that will be obtained, these two aspects are analyzed: the follicular size and the concentration of estradiol.
Each follicle develops an oocyte inside, but it is possible that, at the time of puncture, no oocyte is obtained from some follicles or that some oocytes are immature and, therefore, not suitable for fertilization.
Therefore, the number of mature oocytes recovered after ovarian puncture may be lower than the number previously estimated.
As the maturation stage of the ovarian follicles progresses, they increase in size. For this reason, the gynecologist controls the size of the follicles using transvaginal ultrasound. When a follicle measures around 16-18 mm, it is established that it has developed enough so that there is a mature oocyte inside it. In this way, the puncture will be scheduled 34-36 hours after finding follicles of this size.
Therefore, measuring the size of the follicles will be a way to estimate the number of mature eggs that will be extracted during the follicular puncture.
Blood estradiol concentration
Each mature ovarian follicle can correspond approximately to 200-300 pg/ml of estradiol in the blood. Therefore, taking this information into account, we can estimate the number of mature follicles based on the concentration of estradiol determined by a blood test.
As an example, an estradiol concentration of 3000 pg/ml would make us think that the gynecologist could puncture around 15 follicles, that is, extract around 15 ovules.
Quantity or quality of the ovules?
The purpose of an in vitro fertilization process is to achieve a healthy baby. For this, it is necessary to obtain viable embryos, capable of implanting in the maternal uterus and giving rise to an evolutionary gestation. This is why we can say that quantity is not as important as oocyte quality (and, of course, also of the sperm).
It is true that the greater the number of ovules, the greater the probability of creating viable embryos and, therefore, of achieving reproductive success. However, if the eggs obtained are of poor quality, it will be more difficult to achieve conception even if many have been extracted in the puncture.
On the other hand, if we have fewer ovules but they are of high quality, it is likely that at least one embryo capable of implanting in the uterus and giving rise to pregnancy will be obtained.
On the other hand, we must take into account that the number of ovules does not always correspond to the number of embryos. Of the mature ovules obtained, not all will be able to fertilize correctly and, of those that are fertilized, some will be blocked during embryonic development.
For this reason, it is important to obtain a good number of quality eggs, in order to have a greater number of viable embryos. In this way, these embryos can be vitrified and transferred in later cycles, either because the first attempt was not successful or because they want to have more offspring.
In any case, and by way of conclusion, we must emphasize that it is not only a matter of quantity but also of the quality of the ovules.
FAQs from users
What is the ideal number of eggs for an IVF cycle?
While the success with IVF literally only requires one normal embryo, patient outcomes improve with a reasonable number of eggs retrieved, typically 10-15 mature eggs. Actually, studies have shown that egg quality may be reduced if retrieval results in an excessively high number of eggs. Of the eggs retrieved, approximately 60-80% are mature and of these, about 70-80% will fertilize. Once an embryo divides, it has a 50-60% chance of developing into a day 5 blastocyst which is most optimal for implantation or freezing.
How many follicles are needed for IVF?
After undergoing ovarian stimulation, at least 3 mature follicles should be ready to be punctured. Follicles are considered mature when they are 16-20 mm in average diameter.
Is the quality or quantity of eggs more important in an IVF cycle?
Both aspects are important. However, it is essential that the egg is of good quality, because if the quality is low, it will not matter how many eggs we obtain, since it is likely that none of them will allow pregnancy after fertilization.
My gynecologist tells me that they anticipate getting 4 mature eggs in the retrieval, is that ok?
Under normal conditions, 4 eggs is a low number. However, depending on your situation and age, it is possible that it is a good prognostic number. In any case, the important thing is that these 4 eggs are of good quality. If at least one of them is of very good quality and allows obtaining an embryo capable of implantation, pregnancy will be achieved. In this case, 4 eggs will be sufficient to achieve the objective: gestation.
If you liked this story, you may want to go through this: Collecting a Large Number of Eggs & Pregnancy Chances.
Also, if you are a poor responder, you may enjoy reading the following post: Poor Responders in IVF Cycles – Management & Best Protocols .
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FAQs from users: 'What is the ideal number of eggs for an IVF cycle?', 'How many follicles are needed for IVF?', 'Is the quality or quantity of eggs more important in an IVF cycle?', 'How many do you need for IVF?', 'Do all fertilized eggs result in pregnancy?' and 'My gynecologist tells me that they anticipate getting 4 mature eggs in the retrieval, is that ok?'.
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