Yes. Women are born with all their eggs; they do not produce new eggs in their lifetime. Each month (assuming that a woman is ovulating) one egg matures giving it the potential to be fertilized by sperm. Meanwhile, during each cycle hundreds of eggs are lost without ever achieving such an opportunity. By the time a woman reaches her late thirties, only a small fraction of her eggs remain fewer than 10 percent.

In addition to the problem of decreasing egg number, a woman’s age also affects egg quality. Eggs from older women harden and stiffen, which makes it more difficult for the sperm to enter the egg and also results in more errors as the egg passes down its’ chromosomes. Not only is fertilization is less likely to occur, but those eggs that fertilize are more likely to result in embryos with abnormal chromosome numbers, thereby increasing the risk of genetic problems, such as Down’s syndrome (trisomy 21, having three copies of chromosome 21 instead of the normal two). The frequency and complexity of these errors increase with age.

Consequently, the potential for a woman to produce normally fertilized eggs and resultant embryos drops dramatically as she ages. Given that naturally she only has one opportunity each month to mature an egg (i.e., ovulate), a woman at 40 years of age may have only one chance per year of producing a normal egg!