Egg quality & quantity & the relationship to fertility, infertility and IVF success
- Egg quantity, also referred to as ovarian reserve, is the number of eggs a woman has remaining for the future
- In general, egg quantity is also closely related to age, but it can vary dramatically at any age
- Tests of ovarian reserve are done by fertility specialists to estimate the remaining egg supply
- Antral follicle counts on ultrasound, day 3 FSH testing, and AMH levels are the best tests of ovarian reserve
- The number of eggs obtained with IVF has a strong influence on the chance for success
Can we test eggs for quality?
We can test egg supply with ovarian reserve testing (mentioned above) but we do not have a test for egg quality.
- At this time, the best test of egg quality is female age
- Chromosomal abnormalities in eggs increase significantly with aging
- Poor egg quality is often related to chromosomal abnormalities - aneuploidy
Patients often say: "My eggs are fine, I don't think I need testing for that." When asked how they know the eggs are fine, the most common answers are;
- "Because I get my period every month"
- "Because my gynecologist said my eggs are fine"
However, the gynecologist did not do any tests of ovarian reserve, so the patient got information based on an assumption and not based on data. Or, maybe the patient and the gynecologist did not communicate well and there was a misunderstanding about the "egg issue".
- A 45 year old can have some good quality eggs and still be fertile, although this is rare
- At the other extreme, a 25 year old can have poor quality eggs and be infertile (also rare)
- These are extreme examples. The point is that egg quantity and quality declines significantly as women age.
- IVF success rates and age
When does ovarian reserve and fertility begin to decrease?
The decline in fertility potential in women usually begins in the early 30s and accelerates in the mid to late 30's. Egg quantity and quality in an individual woman can be average for her age, better than average, or worse than average.
When couples try to get pregnant on their own (yes, fertility doctors approve of having a sex life and getting pregnant without our help) a limiting factor will sometimes be egg quality.
She may have regular monthly menstrual cycles and have sex on the perfect day for the sperm and egg to have a date. But if the egg she ovulates is poor quality (a red dot in the figure below) then it will either:
1. Not fertilize
2. Fertilize, but not develop properly to become capable of implanting in the uterus
3. Implant - but then not be "healthy and normal" enough to be able to continue proper fetal development - resulting in a miscarriage.
- When we do ovarian stimulation and intrauterine insemination or in vitro fertilization procedures, the issues are similar.
- With these treatments there also can be an issue of egg quantity as well as egg quality
- If only a few eggs develop in response to the ovarian stimulating drugs, we have a lower chance of success because of a reduced supply (quantity) issue. There could be an egg quality issue as well.
- Number of eggs obtained and success rates with IVF
The drawings and discussion below are to help illustrate issues about the relationship between egg quantity, egg quality, age and fertility potential.
- Dots are eggs
- Green dots are eggs that are "good" enough to fertilize,
develop normally into a quality embryo and result in a healthy baby being born.
- Red dots are eggs that are not "good" enough to fertilize, develop into a quality embryo and jump through all of the hoops in order to become a healthy baby.
A sample from an ovary of a woman of advanced "reproductive age" - for example age 42
Few eggs and a low percentage of quality eggs
This represents a sample from an ovary of a young woman - for example, age 28
Many eggs and a high percentage of quality eggs
For example, if we are doing IVF on 2 women as represented above with the "dots":
- One is 42 with low ovarian reserve, the other is 28 with good ovarian reserve
- We give the ovarian stimulating drugs to both women
- The 42 year old has a low remaining number of eggs - and therefore has a low response to the drugs - and we get 4 dots (eggs)
- The 28 year old has a lot of eggs remaining - and therefore has a high response to the drugs - and we get 14 dots (eggs)
- Even more importantly, we need green dots instead of red dots to have a baby
- The response of the ovaries to the drugs is random - green dots (good eggs) are not more likely to respond compared to red dots (poor quality eggs)
If we (randomly - with our eyes closed) dip a soup ladle into the (42 year old) ovary (upper one) and get 4 dots - are any of them green? It is likely that they would all be red - which would result in a failed IVF cycle.
If we dip a ladle into the soup of dots from the ovary with good reserve (lower one) and get 14 dots - are any of them green? It is likely that at least some would be green - which would then be expected to result in good embryo quality, a successful IVF cycle and a live birth. Perhaps there would also be some frozen embryos that could be used later to have more children.
- Quite often, the reason IVF fails is as simple as "we didn't get a green dot"
The point is not that a 42 year old should not try IVF and a 28 year old should. This is just to illustrate issues related to egg supply, egg quality, resulting embryo quality and chances for success with IVF and other fertility treatments.
Testing fertility potential in the general population (not infertility patients)
Treatment options for women with reduced ovarian reserve: