The average age for girls to get their first period, known as menarche, is 12, according to the U.S. Department of Health and Human Services. However, menstruation may begin as early as age 8 or as late as age 16. Menstruation, the monthly process of shedding the uterine lining, is guided by hormonal changes that result in several signs indicating that a girl’s first period is on its way. Those signs include white vaginal discharge, spotting, breast development and other signs of puberty.
A girl's breasts begin to grow as she enters puberty, and that process extends into the late teenage years. Development may begin with tenderness or small lumps under the nipples of one or both breasts. It is normal for breasts to grow at varying speeds, which results in breasts of different sizes. Breast growth is commonly a hereditary process; therefore, a girl and her mother, sister or grandmother will have similar experiences. According to the U.S. Department of Health and Human Services, girls typically have their first period within two years of beginning to develop breasts.
Physical Signs of Puberty
The growth of body hair is a hallmark of puberty. Girls will notice hair growing under the arms and on the legs. Pubic hair (hair near the vagina) usually begins growing as fine and straight hair that eventually thickens and becomes curly. Additional physical signs indicating a girl is beginning puberty include becoming taller, narrowing at the waist, widening hips and a body shape that is more curvy.
Girls often begin producing a vaginal discharge between six months to one year prior to menarche, according to Teen Health. As hormone levels shift during puberty, an increase in the vagina’s secretions help to maintain healthy sexual organs. The colour and texture of vaginal dischange varies according to a menstrual cycle. The texture may be thick, slightly sticky or thin, with colours ranging from white to clear.
Many girls’ first period consists of small amounts of blood, or spotting, according to the American Congress of Obstetrics and Gynecology. Bleeding or spotting is the most recognisable sign that a girl is getting her period; however, it may take as long as two years for a girl’s period to become regular. Menstrual periods for girls 12 years old may occur every 21 to 45 days and last between three and seven days.
Girls often experience mild cramping, lower back pain, tenderness in the breasts, fatigue, headaches, bloating, food cravings and moodiness both before menstruation (often referred to as PMS, or premenstrual syndrome) and during menstruation.