A woman is born with approximately 2,000,000 primary follicles. Thereafter, the ovary remains inactive until puberty, when about 300,000 remain, with about 1,000 dying each month during a woman's fertile years. After the age of 35, the chances of achieving a spontaneous pregnancy decrease significantly as the number of follicles drops drastically, as does the quality of the oocytes due to reproductive ageing, reaching the menopause with very low oestrogen levels.






