Hey girl! let me take you on a journey on Some Facts About Menstruation Menstruation (also called "period" and "menses") is the monthly flow of blood from the uterus through the vagina. Girls have their first menstruation during their puberty when they are about 1014 years. They then have it about once a month until they reach menopause. Menopause is when a woman stops having periods, meaning she will no longer be fertile and...