Menarche is the first month of menstruation, which is a natural physiologic process that happens on a monthly basis. Menarche usually happens about the age of 12, although it is perfectly natural to have it a few years sooner or later. Menarche occurs during puberty, a period of physical and sexual maturation in adolescence.

Menopause is the natural termination of a woman's menstrual cycle, and it signifies the end of her fertility. Although most women reach menopause by the age of 52, pelvic or ovarian damage may cause menopause to occur earlier in life. Early menopause can also be caused by genetics or underlying conditions.

When a mature egg is released from the ovary, it is called ovulation. After that, the egg travels down the fallopian tube to be fertilised. If sperm are present in the fallopian tube when the egg is released, the egg is likely to be fertilised, resulting in an embryo that can develop into an infant.