A woman reaches reproductive maturity when she experiences her first menstruation, which includes the shedding of the inner-lining of the uterus. This first period occurs during puberty, and at this time, a woman's egg can be fertilized by sperm, and she can reproduce. In men, the first signs of reproductive maturity include enlargement of the testicles and penis, a surge in testosterone and the production of sperm, explains MedicineNet, Inc.
Though menstruation is the dominant sign of reproductive maturity because only then can a woman become pregnant, other changes occur during puberty that signify the coming of menstruation and reproductive maturity as well. The first of these signs is breast development, which begins in girls around 11 years old. The next step is the growth of pubic hair, followed soon by the growth of underarm hair, though some girls begin growing pubic and underarm hair prior to breast development.
Menstruation occurs approximately two and a half years after the onset of puberty. Although menstruation is indicative of reproductive maturity, it is not until women experiences regular menstruation that fertility is achieved. The menstrual cycle occurs for approximately twenty-eight days. It is a cycle that includes the body building up the lining of the womb in preparation for pregnancy, and then shedding it if no egg is fertilized. Fertility and menstruation continue until a woman reaches menopause, at which point she no longer releases eggs, has a monthly period or can become pregnant.