Conventional science has taught women for years that they are born with all of the eggs they will ever have. The theory has been that women are born with one to two million immature eggs at birth, and will slowly begin losing them over the course of their lifetimes.
Many of those eggs will be lost before puberty sets in through a natural process called ovarian follicle atresia, leaving a woman with around 300,000 eggs at the time of puberty. Of those, it is estimated that women may lose as many as a thousand eggs per month over her fertile years. Of the roughly 400 follicles that will reach ovulation over the course of a woman’s fertility, a woman can expect 20 follicles to mature each month with just one egg being released.
Science goes on to tell us that only the best quality eggs will be released and that, over time, the overall quality of these eggs begins to diminish as menopause approaches. This is commonly believed to be the reason why women of an advanced maternal age have difficulty achieving pregnancy with their own eggs.
Despite all of this traditional wisdom, new studies are beginning to suggest that a woman may, in fact, be able to produce new eggs in her lifetime. The theory is based around the existence of stem cells found within the ovaries. This theory stems from a finding back in 2004, when researchers encountered germ cells called oogonial stem cells in the ovaries of female mice. Then, later in 2012, a study conducted by scientists from Massachusetts General Hospital and the University of Edinburgh and published in PLoS Genetics, found the same stem cells inside of a human female’s ovaries.
These cells are capable of dividing and generating new oocytes, which become new eggs. Advanced medical tools allow scientists to see how many times a cell has divided over its lifetime, and if conventional science stands true, all human eggs would have the same number of divisions, as all eggs should be present at birth. However, scientists have found that some of these cells have many more divisions, suggesting that new eggs were forming over the women’s lifetimes.
While the research is still in its infancy and has only been conducted on mice at this point, it suggests that fertility and egg development may continue long after birth.