It's hormones! Hormones trigger your ovaries to produce and release one egg from either your right or your left ovary. This is called ovulation. Before ovulation occurs, your uterine lining is thickening to prepare for a fertilized egg to implant in the uterus. If an egg is not fertilized, then the uterine lining sheds. This is called menstruation or your menstrual period.

Every woman's cycle (the time from the first day of your menstrual period until the first day of your next menstrual period) is different. On average, a woman has her menstrual period for 3-7 days. The average length of a woman's cycle is 28-32 days. This leaves plenty of room for a woman to vary from her neighbor, friend, or co-worker. Women also vary in the severity of symptoms that occur before and during menstruation.

Approximately 85% of women who menstruate report changes in the days or weeks before their menstruation that cause problems that affect their normal lives. This is known as Premenstrual Syndrome (PMS).

During menstruation, the uterus, which is a muscle, contracts and relaxes more than it does at other times in the month. This can produce the uncomfortable feeling of cramps. Using a heating pad or hot water bottle may help ease some of the discomfort. Taking over-the-counter pain relievers such as naproxen, ibuprofen, or acetaminophen may also help. Other discomforts during menstruation may include breast tenderness, bloating, headaches, fatigue, mood swings, and food cravings. Some women will experience these symptoms more than others will, and not every woman will experience all of these symptoms.