Women experience a monthly cycle called menstruation or a period. The lining of the uterus breaks down and leaves the body through the vagina. This has a range of effects on the reproductive system and other organs.
Young girls are often between 8 and 15 years old when they experience their first period. The first cycles might be quite irregular. The average age for onset of menstruation in the United States is 12 years.
Most women will see their period recur every 28 days. However, cycles of 21 to 35 days are also normal in adult women.
Girls over 13 years of age can experience more irregular cycles that range from 21 to 45 days. Hormones regulate these cycles.
Periods typically last for between 3 and 7 days, and the amount of blood loss can vary. They can range in severity between mild, moderate, and heavy.
Not every woman will experience the same premenstrual symptoms. Common symptoms include:
- breast swelling and tenderness
- acne breakouts
- leg, back, or stomach cramping
- premenstrual syndrome
Some women may confuse the symptoms of menstruation with those of early pregnancy, as they can be similar. These include a missed period, breast tenderness or swelling, nausea, frequent urination, and tiredness.
Some women report feeling the symptoms of premenstrual syndrome (PMS). This very common condition can include symptoms such as:
- rapid changes in mood
- social withdrawal
- difficulty concentrating
- breast tenderness
PMS may be caused by changes in hormone or serotonin levels.