Menstruation: What age should first period occur?

Maybe. Most girls begin to menstruate at age 12 or 13. Some girls will start a few years later. However, girls who haven't had their first menstrual period by age 16 — a condition called primary amenorrhea — should be evaluated by a doctor.

If your daughter is of normal height and weight, has developed secondary sexual characteristics — such as breasts and pubic hair — and has no pelvic discomfort, you likely have nothing to worry about. Your doctor may simply advise you to wait for nature to take its course.

However, if your daughter hasn't developed secondary sexual characteristics by age 16 or early changes haven't continued, your doctor may recommend further testing. Possible causes of primary amenorrhea include:

• Pituitary gland disorders
• Disorders of the hypothalamus — an area at the base of the brain that regulates the menstrual cycle
• Chromosomal abnormalities, such as Turner's syndrome or Sawyer's syndrome
• Absence of or abnormal development of reproductive organs