Menarche and the Teenage Menstrual Cycle

Menarche (say "MEN-ar-kee") is a girl's first menstrual period. A first period usually happens after breasts, pubic hair, and underarm hair have begun to grow. Menarche is a sign of growing up and becoming a woman. It can happen as early as about age 9 or up to age 15. The first few periods are usually light and irregular. About 2 out of 3 girls have a regular pattern of menstrual periods within 2 years of menarche.⁴ During the teen years, periods may become longer and heavier. For more information, see Menarche.

Perimenopausal Menstrual Cycle

Perimenopause, which means "around menopause," refers to the 2 to 8 years of changing hormone levels and related symptoms that lead up to menopause. The most common sign of perimenopause is longer, often irregular menstrual cycles that are caused by hormonal ups and downs.

Most women start perimenopause between ages 39 and 51.⁵ Some women begin to notice menstrual changes and premenstrual syndrome (PMS) symptoms in their late 30s when hormones begin to fluctuate and fertility naturally declines. Other women don't notice perimenopausal changes until their late 40s.

Perimenopause is a time of unpredictability. Menstrual and hormone-related symptoms are different for every woman. Some notice few or no changes. And others have severe symptoms that disrupt their sleep and daily lives. As during the teen years, irregular cycles can lead to heavy menstrual bleeding. Other common symptoms include mild to severe hot flashes, insomnia, cloudy thinking, headaches, heart palpitations, mood swings, irritability, depression, and anxiety. Some of these symptoms can also be related to aging and other life changes. See your doctor to discuss your symptoms, whether you want symptom treatment, and which therapies you can consider.

See a doctor for menstrual bleeding that lasts longer than 7 days or for cycles that are shorter than 21 days or longer than 35 days. For more information, see the topics Dysfunctional Uterine Bleeding and Menopause and Perimenopause.