The first menstrual period, also called menarche, begins at different times for young girls. While no one can precisely predict the exact timing of a first period, there are some biological signs that may indicate when it will likely occur. During the period itself, a girl may experience symptoms such as cramps or emotional reactions in addition to the obvious release of blood from her uterus.
Menstruation occurs in response to female hormones that help the body prepare to be able to have a baby. Before the period comes ovulation, the release of an egg from the ovaries. Most girls don't notice their first time ovulating, since ovulation typically produces no symptoms. However, some girls may feel a slight cramp or twinge on the side where the ovary releases the egg. About 14 days after ovulation, the uterine lining, which has been building up in preparation for a possible baby, sheds and releases blood stored in the uterus. This blood exits via the vagina and begins the girl's first period.
The two major pre-period symptoms are breast growth and the growth of armpit hair. Breast growth occurs in stages with the first sign being an elevation of the nipple, or breast budding. The breasts will grow over an average of two years, according to OB/GYN.net, until she has breasts large enough to fit into a real bra with an actual cup size. Once she's wearing a real bra and armpit hair appears, the first period is about three to six months away. About six months before her first period, a girl may also notice a white vaginal discharge.
When menstruation is about to begin for the first time, a girl may notice symptoms such as cramps, headache or irritability. These are normal pre-period symptoms and may continue to occur just before the period throughout the girl's life. When the period begins, it may start as a small trickle of blood or may seem like a lot of blood. The average amount of blood lost during menstruation is about 2 tbsp., according to the Nemours Foundation.
According to the Nemours Foundation, a girl will typically get her first period between the ages of 8 and 14, when she enters puberty. The most common age is about 12. The first period starts the menstrual cycle, which can range from 21 to 45 days and may remain irregular for years before settling into a regular adult pattern of 28 to 32 days between periods.
Over-the-counter pain remedies, exercise or a warm bath can help ease menstrual cramps caused by the first period, explains MayoClinic.com. The girl should use a sanitary pad or tampon to collect the blood. A menstrual cup is another option for collecting and removing the expelled blood. If a girl expects that she may begin having periods soon, she should carry a pad or tampon with her in her purse at all times and make sure the bathroom at home is well-stocked with everything she might need.