Almost all In Vitro Fertilization (IVF) procedures include a phase called ovarian stimulation through ovulation induction. The ultimate goal of such stage is to trigger the maturation of multiple eggs in one cycle, instead of one egg as it normally occurs. It allows us to retrieve a higher number of eggs, thereby increasing the success rates of IVF.
Many IVF patients who are about to start the stimulation phase wonder what is the average number of eggs considered good for IVF to be success. Actually, there is not a unique answer to this question, as we will explain in the following sections.
The different sections of this article have been assembled into the following table of contents.
Ovarian response during IVF cycles
The process of ovarian stimulation used in all IVF/ICSI cycles involves the administration of exogenous hormones to monitor the ovarian cycle. The stimulation phase takes about 8 days, but your doctor may decide to extend this timeframe to the previous cycle by prescribing contraceptive pills.
The ovarian response during IVF cycles varies from woman to woman depending on the characteristics of each patient, the medication protocol, the cause of infertility, etc.
Keeping this in mind, we can distinguish three types of responders to IVF meds:
- 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 are egg donors. Even though it occurs rarely, there have been cases in which over 50 eggs have been retrieved.
During the stimulation phase, you should visit the fertility specialist regularly to monitor your response to IVF meds. Depending on the results, he or she may readjust the dose administered or change the protocol.
One should note that being included in any of the groups described above does not translate into an underlying problem. In other words, a 45-year-old woman is expected to be a poor responder. In fact, chances are that she's not a poor responder, but that the number of eggs retrieved is so low because her egg count is poor due to age.
For instance, a 20-year-old girl is expected to have a high response to medications. For such reason, your doctor will pay close attention to the dose administered. It's uncommon that these patients turn out to be poor responders.
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What's a good number of eggs retrieved?
Egg retrieval, medically known as ovum pick-up or follicle puncture, is a surgical procedure whereby mature eggs are harvested from the ovary. The purpose of this surgical procedure is to collect the eggs when they are at metaphase II, considered the optimal state of maturation for retrieval and fertilization.
In order to schedule follicle puncture in the right moment, that is, before spontaneous ovulation, and be able to predict the number of eggs able to be retrieved, two aspects are evaluated: follicle size and levels of estradiol.
Each ovarian follicle contains an egg cell within. However, oftentimes the follicle is empty at the time of egg retrieval, or it contains eggs but they are immature. In other words, fertilization is not possible in these cases.
In short, the number of eggs retrieved after egg retrieval may be lower than the number of follicles seen on ultrasound or estimated in accordance with the amount of estradiol in blood.
According to follicle size
Your doctor will measure the size of your follicles through ultrasound scan. As egg mature, follicles increase in size.
When an ovarian follicle reaches the size of 16-18 mm, it is considered mature enough to contain a mature egg cell within. At this point, your doctor will schedule the follicle puncture procedure within 24-48 hours after seeing follicles of that size.
By doing this, we can estimate the number of mature eggs that will be ready to be retrieved during the collection process.
According to estradiol levels
Approximately, each mature follicle equals 200-300 pg/ml of estradiol. Keeping this in mind, it is possible to estimate the number of mature follicles to retrieve based on the estradiol levels.
Estradiol levels of 3000 pg/ml typically correspond to about 15 follicles. In other words, such amount of estradiol indicates that about 15 eggs will be ready to be retrieved.
Egg quality vs. quantity
The ultimate goal of every in vitro fertilization process is to achieve an ongoing pregnancy. But first, viable embryos must be created. And by viable embryos we mean embryos that are able to attach to the uterus and give rise to a new pregnancy.
So, concerning the title of this post, What Is a Good Number of Eggs Retrieved for IVF?, the answer is simple: quantity is not as important as quality.
However, it is true that, the higher the number of eggs retrieved, the higher the chances of creating viable embryos with implantation potential. But, if the quality of the eggs collected is low, a pregnancy won't occur even if a high number of eggs were retrieved.
If only 2 eggs are retrieved but they are of optimal quality, chances are that we are able to create an embryo with a great implantation potential, able to lead to a successful pregnancy on the first attempt.
As one can see in the chart below, age also plays a major role when it comes to determining the number of eggs retrieved:
On the other hand, we should keep in mind that the number of eggs does not always match the number of embryos. Out of the eggs collected, not all of them will be fertilized.
In conclusion, obtaining a good number of high-quality eggs is essential, as it is likely to translate into a great number of viable embryos. In these cases, a percentage of these embryos can be cryopreserved to be transferred in subsequent cycles, should the first attempt be unsuccessful or because you want to have more children.
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.
What if the number of eggs I produce is insufficient for IVF?
In order to be able to fertilize more than one egg cell in the same IVF cycle, women's ovaries are stimulated using fertility drugs. The number of eggs required depend on the technique used. For IVF, it is enough with 1 or 2; whilst for IVF/ICSI, we should have around 10 eggs ideally. Oftentimes, due to a varied set of causes, the ovarian response of some patients is inadequate and the number of eggs collected is too low (below 5). In such cases, we can turn to the following strategies:
- To cancel the cycle before egg retrieval and start a new stimulation cycle with a different stimulation protocol.
- To freeze using egg vitrification technique the eggs to collect a higher number of eggs in subsequent cycles.
- To freeze using embryo vitrification technique the resulting embryos in order to transfer 2 in the subsequent cycle.
In short, it depends on the history of each couple.
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.
How many do you need for IVF?
We can consider 15 as a good number of eggs for IVF. A study found that there is a strong relationship between the live birth rates and the number of eggs retrieved in one cycle, but this relationship starts to decline beyond 20 eggs.
Do all fertilized eggs result in pregnancy?
It is estimated that, on average, between one-third and one-half of all fertilized eggs never fully implant. So the answer is no, not all embryos are able to implant, hence the importance of retrieving good quality eggs.
Suggested for you
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?', 'What if the number of eggs I produce is insufficient for IVF?', 'How many follicles are needed for IVF?', 'How many do you need for IVF?' and 'Do all fertilized eggs result in pregnancy?'.