Overview

The menstrual cycle is the series of changes in the body to prepare for a possible pregnancy. Menstruation most often begins between the ages of 11 and 15.

If you haven't had a first period by age 15, it's called primary amenorrhea. This is different from infrequent or light menstrual cycles, which are very common in teens, particularly in the first couple of years after menstruation begins. Primary amenorrhea is also different than if you start having periods, but then stop having periods for at least 3 cycles.

You can still become pregnant even though you aren't menstruating. Practice birth control if you don't want to become pregnant.

What causes it?

Causes of primary amenorrhea include:

• Problems with the structure of the vagina, such as skin covering the opening of the vagina (imperforate hymen).
• Absence of or an abnormal pelvic organ, such as the uterus or ovaries.
• Very low or very high body weight.
• Eating disorders, such as anorexia, bulimia, or fad dieting.
• Intense exercise.
• Stress.
• Malnutrition.
• Chronic diseases, such as diabetes, anemia, congenital heart disease, or thyroid disease.
• Inherited diseases, such as Turner syndrome.
• A condition that causes a hormone imbalance that interferes with normal ovulation (polycystic ovary syndrome).
• Medicines or medical treatment in childhood that may have damaged the ovaries, such as chemotherapy or radiation treatment for cancer. Chemotherapy or radiation treatment in adulthood may cause irregular cycles.

How is it treated?

Treatment depends on the cause. If the cause is a physical problem, such as imperforate hymen, then you may have surgery. For other causes, your doctor may prescribe hormone therapy to help control your cycle. It can also help protect your bones. Your doctor also may prescribe calcium supplements for bone health.