Egg Quality and A Woman's Age
You may have heard that female infertility is likely to increase with age, making it more difficult for older women who are trying to get pregnant. While there are many factors that contribute to the decline of female fertility with age, including the possibility of premature menopause, poor egg quality can contribute to the cause of infertility. However, egg quality alone does not guarantee infertility, and there are many infertility treatment options available precisely for dealing with this factor to help increase fertility.
What is Egg Quality?
While it may be true that women have limited quantities of eggs which decline with age, the quality of these eggs is also crucial to conception. The combination of egg quantity and egg quality constitutes a woman's ovarian reserve.
Egg quantity simply refers to the number of eggs a woman has. A woman is born with a certain amount egg follicles, the number of which will usually be between 300,000 to 400,000 by the time a woman reaches puberty. During a woman's monthly menstrual cycle, approximately 20 follicles will begin their journey to become mature eggs. However, only 1 or 2 of these eggs will succeed in maturing into quality eggs that are ready for fertilisation.
Egg quality thus refers to how prepared an egg is to grow, divide, and develop inside the embryo as well as how prepared it is to be fertilized. This is largely determined by two factors: the number of chromosomes present within a given egg, and the energy supply of the mitochondria of an egg.
The energy provided by the mitochondria (organelle components of a cell) is necessary to ensure the growth an egg once it has been fertilized. Insufficient energy will likely lead to a miscarriage. Abnormal chromosomes are a natural occurrence; some of your eggs will be so-called good eggs, while some will not.
Egg Quality and Age
Age is among one of the biggest factors affecting egg quality in a woman. Because a woman has a finite amount of ovarian reserve, as she ages the quantity as well as the quality of eggs will naturally decline.
When a woman is in her 20s or 30s, she will likely have a larger proportion of good eggs available for fertility. However, when a woman is in her late 30s and 40s, the proportion of bad eggs will likely be greater.
What causes poor egg quality is often a decrease in the energy supplied by the mitochondria, which tends to decline with age. This means that eggs which may have been considered healthy at a younger age cannot support fertilisation and growth.
Indeed, the percentage of couples experiencing infertility begins to rise when individuals are in their mid 30s. Approximately 11% of couples around the age of 35 have fertility difficulties, which increases to 33% by the age of 40. By the age of 45, 87% of couples will statistically be experiencing infertility. Women between the ages of 15 to 25 are believed to have a 40% chance of conceiving every cycle, while women over the age of 40 have less than 25% chance of getting pregnant.
Egg Quality and Fertility
Egg quality is directly related to fertility. Egg quality will determine a woman's ability to get pregnant as well as stay pregnant and avoid pregnancy complications. Poor egg quality can result in an egg not being properly implanted in the uterus even though it has been fertilized. However, eggs that are successfully implanted may not be healthy enough to sustain themselves and result in miscarriage. Abnormal chromosomes, which are more likely to be present in older women, can result in genetic abnormalities such as Down's syndrome.
Testing Egg Quality
There are two common fertility tests available when it comes to egg quality:
- The Day 3 FSH Test. This fertility test is used to analyze levels of FSH (follicle stimulation hormone) in the blood stream. The test is taken on the third day of a woman's menstrual period. High FSH levels may indicate poor egg quality since the presence of a successfully matured egg during ovulation would hinder the production of FSH.
- The Chlomid Challenge Test (CCCT). This test is conducted on the tenth day of a woman's menstrual cycle. This follows a dose of chlomid which is given prior to the test date. The analysis provides a more accurate and in-depth look at FSH levels.
Infertility Treatment Options
Fertility drugs are available to promote ovulation in women with poor egg quality. Fertility drugs such as Clomiphene, Human Menopausal Gonadotrophin, and Bromocriptine work by stimulating hormones that assist in the maturing process of an egg and release it from the ovaries on a monthly basis.
Assisted Reproductive Techniques (ART) such as IUI and IVF combined with superovulation drugs that help increase the amount of eggs retrieved from a woman's body may also be used. However, the success rates of these techniques decline as a woman ages. Whereas a woman between the ages of 20 and 30 may have a 15% to 20% chance getting pregnant using ARTs, a woman over the age of 40 may have a likelihood of 5% to 8%.
In cases of persistent difficulties getting pregnant, finding an egg donor may be recommended.
The future is bright for fertility treatments of egg quality. Current studies are looking to cytoplasmic and nuclear transfers of healthy cell components from donor eggs to improve the quality of eggs.
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