Which Side of the Coin Are You on Regarding Possible Postnatal Oogenesis?

It is well known that oocytes are produced during fetal development and that the total number of primary follicles is determined at birth. In humans, there is a constant loss of follicles after birth until about two years of age. The number of follicles is preserved until the resumption of meiosis at puberty and there is no renewal of the oocytes; this dogma was maintained in the last century because there were no suitable techniques to detect and obtain stem cells. However, following stem cell markers, several scientists have detected them in developing and adult human ovarian tissues, especially in the ovarian surface epithelial cells. Furthermore, many authors using different methodological strategies have indicated this possibility. This evidence has led many scientists to explore this hypothesis; there is no definitive consensus to accept this idea. Interestingly, oocyte retrieval from mature ovaries and other tissue sources of stem cells has contributed to the development of strategies for the retrieval of mature oocytes, useful for assisted reproductive technology. Here, we review the evidence and controversies on oocyte neooogenesis in adult women; in addition, we agree with the idea that this process may occur in adulthood and that its alteration may be related to various pathologies in women, such as polycystic ovary syndrome, premature ovarian insufficiency, diminished ovarian reserve and several infertility and genetic disorders.