There are different kinds of infertility experienced by women and the causes of infertility in women are also many and varied. As 40-50% of all infertility cases are caused by female infertility factors, there is a need to examine the causes behind it. One of the most important causes of female infertility is age. Typically, when a woman is born, over 400,000 eggs are present in each ovary. This quantity decreases over time and this continues till a woman reaches 50 years. At this age, menstruation stops and the menopause period starts.
Age is one issue, but the real fertility issue is egg quality and quantity and not the number in a woman’s age. Egg quantity and quality in an individual woman can be average for her age, better than average, or worse than average. We know that egg quantity and quality declines in the mid to late 30s and falls faster in the late thirties and early 40s.
Female Age – Egg Issues
- Successful pregnancy outcome is very much related to female age – when using the woman’s own eggs.
- When donor eggs are being used, the age of the egg donor is the important issue.
- With egg donation, the age of the recipient woman has very little impact on the chance for successful pregnancy.
- Therefore, the age of the egg is very important, but the age of the uterus is not.
- Much of the problem is due to an increased percentage of chromosomally abnormal eggs with aging
Increased risk of Miscarriage with age
As the age of women increasing they also have a higher chance of losing the pregnancy (miscarriage).
The sperm and egg each contain 1/2 of the chromosomes necessary to make a complete human being. In fact, to describe it in lay terms, the process of making sperm and eggs is nothing more than the packaging of different combinations of chromosomes so that they can be “mixed” together with another egg or sperm to make different varieties of humans.
Women are born with all the eggs that they will ever have in their lives (with the chromosomes inside). Men, on the other hand, make fresh sperm continuously throughout their whole lives. It takes approximately 90 days for a sperm to be made and to reach maturity. This is an extremely important difference between the sexes because, for example, if a 35 year old man and a 35 year old women attempt to achieve a pregnancy, they are basically trying to combine a 35 year old egg with a 3 month old sperm.
The longer an egg sits around in the ovary, however, the more likely it is to develop abnormalities in its chromosomes. If an egg with abnormal chromosomes is fertilized, then the chances are greater that the resulting pregnancy will end in miscarriage. In fact, chromosomal abnormality is the single most common cause of miscarriage. From many studies, we know that at least 1/2 of all miscarriages are due to abnormal chromosomes. A young women (in her 20s), therefore, has only a 12-15% chance of having a miscarriage each time she becomes pregnant. A women in her 40s has, however, a 50% risk of miscarriage.