The importance of egg quality in women trying to conceive can not be stressed enough. Women are born with a certain, and finite, number of eggs. Even though there may be more eggs present in the ovaries than a woman will ever be able to ovulate and ‘use’, having a lot of eggs doesn’t necessarily translate into having GOOD eggs. Most women believe that if you have eggs, you will get pregnant. Makes sense right? Sadly, this is not the case. This is because egg quality plays a bigger role than egg quantity.
What exactly do we mean we talk about “egg quality”? Egg quality refers to the ability of your eggs to develop into embryos once they have been fertilized. An egg must have the proper number of chromosomes, which happens during a process known as Meiosis. If there is an error in meiosis, the egg could have more or less chromosomes than it should, and thus not be a ‘good’ egg. This not something that you have any control over via diet, medications, etc. The fact is that Mother Nature is imperfect and some eggs in your body just don’t have the right number of chromosomes.
The eggs also need to have an energy source in order to be able to divide after fertilization. Tiny organelles called mitochondria are responsible for the production of the energy needed by the embryo to divide. If you do not have good quality mitochondria, due mainly to advanced maternal age, the embryos will eventually run out of energy and stop dividing. This is known as “stalling”. In this case, the embryos can not activate their embryonic genome and the embryos stop developing. These embryos are incapable of creating a viable pregnancy.
So can egg quality be detected at the time of retrieval? Yes and no. If ICSI is being performed, the embryologist can get a glimpse of the actual egg and will be able to tell how the egg quality is morphologically. During ICSI, the embryologist must strip the cumulus cells from the egg to check for maturity. Only mature eggs, those with a polar body, can be attempted to be fertilized.
Poor quality eggs may have an abnormal appearance; granular cytoplasm, vacuoles, smooth endoplasmic reticulum, or dark areas within the cytoplasm. They may also notice that the eggs are very fragile and that the membrane that surrounds the egg offers very little resistance upon injection. These are all clues to the embryologist that the quality of the eggs is decreased. Fertilization may be compromised in these embryos and the number of degenerate eggs after ICSI may be increased. Good quality eggs, by contrast, have smooth, healthy looking cytoplasm that is free of vacuoles or organelles. They also provide a good resistance upon injection of the sperm and typically fertilize very well.
Unfortunately, if natural insemination is the method of fertilization, the egg is not actually assessed and it is not until fertilization check that a sense of egg quality can be ascertained. .
Unfortunately, because egg quality is not extensively known, there are only a few treatments we can do to help increase quality, and these may or may not help. One major problem is that there is no way of testing egg cytoplasmic quality - either clinically, or in the research lab at present. Also, it is important to remember that egg quality is greatly affected by your age. As you age, your eggs will begin to decline in quality as well as in number. By the time you are in your late 30s or early 40s, you will probably have more poor quality eggs available than good quality eggs. Egg freezing in your 20’s and early 30’s is one way of preserving your eggs to help counter indicate the effects of age on egg quality.
If you are concerned about egg quality, please contact one of our physicians to discuss the options currently available for helping to improve or preserve egg quality.
Liza has been an embryologist at InVia Fertility Specialists since 2002. She completed her studies, first in animal science at Southern Illinois University, followed by clinical embryology/reproductive genetics at Eastern Virginia Medical School. Her interests include reproductive genetics, fertility preservation, and mitochondrial function in the human oocyte. She loves being a part of helping others achieve and experience the joy of becoming a parent. Seeing the end result .your baby.makes all the hours in the lab worth it!