Antonio Forgiarini, gynaecologist at Next Fertility Valencia, tells us in this video what are the causes of poor oocyte quality:
Causes could be different and a lot of them. I think the principal cause is the time. Oocytes are cells that they don't rejuvenate, they don't regenerate, so we start our life with these cells and they follow through the years to the menopause, so they're exposed to pollution, to oxidative stress, to radiations, to a lot of damage that can lower the quality. Obviously, there's some pathologies (like endometriosis or like some cancers, chemotherapy or radiation) that could lower more and more and more this quality.
https://youtu.be/jA2-bSDLwPM