Menstrual cycle is one of the later stages of puberty seen in girls. The first menstrual cycle is known as "menarche" and in human beings the average age of menarche is twelve years. In the United States it is around twelve and a half. However this is an average and depending on the individual may vary from as early as eight years to as late as . Several factors such as nutrition, environment and genes may effect the actual age when the menstrual cycle sets in. What the menstrual cycle does signify is that the development from child to adult is complete, at least physically and may signify fertility as well. Menstruation is a phase in the menstrual cycle along with follicular phase, ovulation, luteal phase and ischemic phase.
