Egg quality decline is the most important cause of age-related infertility. Egg quality refers to the ability of the egg to create a chromosomally normal embryo. Each egg has 46 chromosomes, 23 from each parent. In order for the egg to prepare for fertilization, it must discard 23 chromosomes in order to make room for the 23 chromosomes brought by the sperm. Failure to correctly discard 23 chromosomes leads to a an embryo with the wrong number of chromosomes, medically referred to as aneuploidy.
There is no test for egg quality, but we know it to be closely correlated to age. For example women in their 20’s have a 20% chance of having a live birth with each month of timed intercourse, a rate that drops