When should I expect my daughter to have her first period?

Half of all girls within the United States experience their first period^[1] before their 13th birthday. However, it's not terribly unusual to find a girl who began menstruating when she was as young as 9 or as old as 17.

In order to put the age issue into perspective, the following statistics may be helpful: 10% of girls menstruate^[2] by the time they're 11 years old; 90% of girls menstruate by the time they turn 14; and 98% of 15-year-old girls menstruate. If your daughter falls outside this age range, she should be examined by a pediatrician, just to make sure she doesn't have a medical problem.

10% of girls menstruate by the time they're 11 years old; 90% of girls menstruate by the time they turn 14; and 98% of 15-year-old girls menstruate.

Research has shown that African-American girls typically menstruate at the earliest age, followed by Hispanic girls and then non-Hispanic White girls. (Interestingly, there aren't any particularly reliable statistics for other ethnic groups.) Your doctor will take these facts into consideration when evaluating your daughter's health.

What is an average menstrual flow?

As with adult females, the average length of menstrual flow^[3] for adolescent girls is 7 days or less. During her period, your daughter is likely to use between three and six pads or tampons per day. If her flow is significantly above this amount, you should contact your pediatrician.

For example, a heavy flow requiring changes of menstrual products every 1 to 2 hours is excessive, especially if the flow lasts longer than 7 days. Not only could this condition lead to anemia^[4], light-headedness, or even fainting, it could also be a sign of polycystic ovarian syndrome^[5], anorexia, tumors, other chronic illnesses, or side effects from medication, so have it checked out.

How does an adolescent girl's period differ from that of an adult woman?

A girl's first period may be a brighter red than what you're used to seeing, and it likely will consist of a smaller amount of blood. In fact, your daughter's first period may really be nothing more than some spotting. But as her menstrual cycle continues, her periods are likely to become more pronounced and may remain irregular the first year.

Can my daughter become pregnant as soon as she starts menstruating?

For the first year or so after your daughter begins menstruating, she likely will not be ovulating. However, it's important to note that no girl who has just started having periods should rely on this fact in the expectation that she won't become pregnant if she has sexual intercourse^[6]. Rather, she needs to be mindful of the safe-sexprecautions I spell out in other parts of this book.

• [1] Refers to the periodic bleeding that occurs monthly from the uterus. Also known as the menstrual cycle.
• [2] The release of the menstrual blood from the uterus and out of the vagina.
• [3] The amount of blood that exits the vagina during a menstrual cycle.
• [4] A medical condition characterized by a low blood count, which means that the patient does not have enough red blood cells. Anemia is sometimes seen in females who experience heavy menstrual bleeding. Symptoms often include fatigue and pale skin, and may include shortness of breath and chest pain.
• [5] A common hormonal disorder seen in young women and female adolescents that involves a variety of symptoms. Classic symptoms include infrequent menstrual cycles, acne, excessive hair growth, obesity, and a cystic appearance of the ovaries on sonograms.
• [6] A very light, scanty amount of bleeding from the vagina that can be bright red or dark brown in color. Often this kind of bleeding is seen at the very beginning or the very end of a woman's menstrual cycle.