Aging and Fertility
Time waits for no man. Or woman. The tendency to delay childbearing is one of the leading causes of infertility today and has resulted in an increasing number of women seeking help. This age-related decline in fertility is due to the aging of the egg and decreased embryo quality.
Women are born with all the eggs they will have, unlike sperm, which are replenished throughout life. The peak number of eggs (6,000,000) occurs when the female fetus is 20 weeks old. By birth, this has declined to 2,000,000. At puberty this number is down to 400,000. This process (atresia) continues throughout reproductive life and results in the ovulation of about 500 eggs during that span.
The best quality eggs ovulate first. Certain factors like smoking can accelerate the atresia. Over time, less optimum eggs are available, thus leading to infertility, increased miscarriages, and chromosomal abnormalities, such as Downs syndrome. The risk of miscarriages increases from 10% below the age of 35-40% above the age of 40.
Therefore the age of the female partner and the ovarian function are the two most important factors.
Tests of ovarian reserve are widely used to determine the prognosis for women seeking fertility. These include blood tests and ultrasound studies. Assisted reproductive technologies (like in vitro fertilization) are available but cannot overcome the age-related decline in fertility. Therefore using donor eggs or freezing a womans own eggs (before age 35) are now the alternatives receiving attention.
An age related decline in fertility is known to occur in men as well. To date, it was widely accepted that men can father children into their 70s. However new studies indicate an increase in diseases like autism and even schizophrenia can be linked to the aging of the sperm.
While it is not possible to turn back the clock, making informed choices will help optimize fertility potential.