When a woman reaches sexual maturity, her ovaries will have approximately 400-500 follicles growing and developing. During a menstrual cycle, there are usually 20-30 follicles that enter the growth cycle. During ovulation, one follicle will mature and ovulate, and the egg will live for 72 hours after ovulation, during which time the egg and sperm will be able to unite and develop, leading to pregnancy. The number of follicles growing on the ovaries during sexual maturity is not constant, sometimes the number of follicles can be reduced due to genetics, hormonal changes or adverse effects such as poor nutrition, fatigue, smoking and alcohol. If a woman is not able to grow and ovulate with mature follicles, she needs to go to the hospital for timely examination and treatment. Follicular development in women during their reproductive years is affected by changes in hormone levels secreted by the pituitary gland, and follicles stop developing in women after menopause.