Egg count is one factor in age-related fertility decline. The other—and most important—factor is egg quality. Egg quality refers to the state of an egg as genetically normal or abnormal.
The eggs inside your ovaries are “primordial,” or immature eggs. As you ovulate, they go through another phase of cell division, known as meiosis. Older eggs are more likely to accumulate errors in their DNA during that division process, leading to genetically abnormal eggs.
Once a cell’s DNA is degraded, it can’t be fixed medically or “healed.” In other words, once an egg becomes abnormal, it can’t become normal again—egg quality cannot be improved. Egg quality is fairly black-and-white—either an egg is genetically “normal” (euploid) or it’s not (aneuploid), and as women age, a higher and higher percentage of their eggs become abnormal.
Since DNA is like an instruction manual for our cells, any damage to your DNA can prevent that cell from doing what it’s supposed to do—which, in the case of the egg, is make a healthy baby.