So you had your In Vitro Fertilization (IVF) egg retrieval yesterday and just got a call from your clinic with your egg count results.
The nurse on the other end of the line told you that of the 13 eggs retrieved, and nine were mature. What does this mean? Is it enough for a baby? Well, it depends.
Let’s get into it.
What is the average number of eggs retrieved during an IVF egg retrieval?
This answer totally depends on the woman undergoing the egg retrieval, so it doesn’t make sense – and wouldn’t be accurate – to give an average.
But if you insist, we can share highs and lows – doctors usually won’t pursue a traditional IVF cycle (which includes the egg retrieval procedure) if they think they’ll get fewer than two eggs, so let’s use two as our low (though some doctors won’t even go this low).
Some young women with a robust egg reserve, or women with Polycystic Ovary Syndrome (PCOS), who have many egg-containing follicles, can have more than 40 eggs retrieved at one time!
There is plenty of variation within this 2-40 range, mostly due to the woman’s age having the egg retrieval.
What is a good number of eggs retrieved for IVF?
Again, this depends on the woman’s age and the number of children she would like to have.
Because the younger the woman, the better quality her eggs, a younger woman could have the same chances of getting pregnant with fewer retrieved eggs than an older woman with more retrieved eggs.
As a rule of thumb, however, having about ten to 12 mature eggs after egg retrieval (not all eggs retrieved will be developed or mature enough to fertilize) is a good number of eggs and will give a woman a good chance of having at least one normal embryo, which gives a woman a 65 percent chance of pregnancy.
The above figure is 65 and not 100 because not all normal embryos will lead to pregnancy, so having several normal embryos available for transfer in case of a failed transfer yields the best chances of success. In fact, RMA research has shown that women with three normal embryos have a 95 percent chance of pregnancy.
Now, if a woman wants to have two children, 12 mature eggs will likely not be enough unless she is young, and most eggs result in genetically normal embryos.
For simplicity’s sake, if 12 mature eggs are usually enough for one normal embryo, which has a good chance (65 percent) of leading to a pregnancy, 24 mature eggs would be a good number for a woman who wants two children.
Also, keep in mind that pregnancy rates will also depend on the overall egg quality of the eggs retrieved during one particular IVF cycle. Because every woman has normal and abnormal eggs, no matter her age, each ‘batch’ of eggs recruited during each IVF cycle will vary in its genetic makeup and yield varying qualities of embryos. Some cycles will result in more normal embryos than other cycles.
Do more eggs retrieved mean a higher success rate?
Most fertility doctors would agree that the more eggs you have retrieved, the higher your chances of success – as in pregnancy and live birth.
Despite some research that shows success rates plateau when a very high number of eggs is retrieved (in the mid to high 20s and beyond) in one cycle, most traditional IVF doctors still prefer moreover fewer eggs (in minimal stimulation IVF, or mini-stim IVF, doctors are less concerned with the number of eggs).
For example, 7 eggs retrieved is better than 3 eggs retrieved, 10 eggs retrieved is better than 7 eggs retrieved, and 13 eggs retrieved is better than 10 eggs retrieved. Getting into high numbers in the 20s or even 30 eggs retrieved is not bad. Still, it does signify the woman may have, as mentioned earlier, PCOS, which could mean her eggs are of poorer quality than a woman without the condition, but this is not always the case.
Why is more better? As we mentioned above, not all eggs are genetically normal and thus will not lead to genetically normal embryos, pregnancies, or births. The more eggs you have to start, the higher your chance of having one or two normal embryos that result in pregnancy. This process relates to IVF attrition.
What is IVF attrition?
IVF attrition is the unfortunate but totally normal process of diminishing odds of success.
At every stage of the IVF process (and there are many!), there is a chance of failure, making IVF a numbers game – the higher your egg number to start, the better the chance you’ll get to one normal embryo that leads to a healthy pregnancy and live birth after all steps are done.
So what are the steps?
First is egg retrieval – in addition to a majority of mature eggs retrieved, most women will have some immature eggs retrieved, too, which can’t be used. For example, say you had 19 eggs retrieved but only 15 mature – that’s a loss, or attrition, of four eggs.
Next is fertilization – not all eggs will fertilize with sperm. On average (depending on the woman’s age), about 80 percent of eggs will fertilize. So if your 15 mature eggs, let’s say only about 12 fertilize.
Next is blastulation – how many fertilized eggs, now called embryos, will reach the all-important blastocyst stage, necessary for Preimplantation Genetic Testing for Aneuploidy (PGT-A), which gives doctors a good idea of the reproductive success of each embryo? About 30-50 percent of embryos will reach this stage, so we’re now down to six.
Now comes the PGT-A testing – how many embryos will test normal? This depends mostly on the woman’s age since eggs are paused in the process of going from a full set of DNA to a half set to combine with sperm. Eggs get worse at restarting that process as time goes on. There will also be a loss here. Let’s say from your six embryos, only three tested normal. Since we know abnormal embryos don’t usually lead to pregnancy or result in miscarriage or an affected child, evidence-based doctors only transfer normal embryos.
The last attrition stage is implantation. As mentioned above, only about 65 percent of normal embryos will lead to pregnancy, so a woman with a normal embryo could still fail to get pregnant on the first transfer – but remember from above, her chances of pregnancy with three normal embryos is 95. Percent!
Do IVF medications improve egg count?
While medications taken during IVF help grow all of the eggs in the batch of eggs your body has already selected for that cycle (a woman’s body decides on a set of eggs to compete for ovulation each month), these medications don’t produce more eggs or direct your body to recruit more eggs.
In other words, the medications work with what you already have; they don’t increase your available egg count per cycle.
This is why doctors will suggest using donor eggs for women with advanced maternal age or those with Diminished Ovarian Reserve (DOR) – because they can see, based on bloodwork and a transvaginal ultrasound examining the egg-containing follicles inside the woman’s ovaries, that her egg count is extremely low and medications cannot improve this. Knowing the attrition rates explained above, doctors understand the chances of live birth for a woman who can only develop a few eggs each cycle are very low.
What is the benefit of IVF, then, you ask? Well, in a natural cycle, though your body recruits a batch with many eggs, only one egg will grow large enough to ovulate, and all others, regardless of reproductive potential, will be lost! In IVF, medications help all the eggs in any given batch develop, so they can all be used for reproduction, making the process much more efficient.
Ultimately, the more eggs you have retrieved, the better, but age is a big factor here.
Because eggs deteriorate with time, younger women tend to have better quality eggs than older women, so even if a younger woman has fewer eggs retrieved than she hoped, the chances of her eggs fertilizing, blastulating, and leading to a normal embryo and pregnancy are good.
Plus, every ovary is different, so comparing your egg retrieval numbers to your friend’s is not the most productive thing to do.
If you have too few eggs retrieved in one cycle (say less than 12 mature eggs), you can undergo another cycle (your body releases a new batch every month!) to get your total count up. This is very common in IVF, so don’t think you’d be the first patient to try this tactic.
As with most difficult things in life, persistence is the key!