Your Reproductive Cycle
Menstruation is a key part of your reproductive cycle. An average menstrual cycle lasts 28 to 30 days, counting from the first day of one period to the first day of the next. Normal cycles can vary from 22 to 35 days.

Each month, after day 5 of your cycle, the lining of the uterus (endometrium) begins to grow and thicken to prepare for a possible pregnancy. Around day 14, an egg is re-leased from one of your ovaries. This is called ovulation.

On about day 28, if an egg is not fertilized, the endometrium is shed by bleeding. This bleeding is your menstrual period. Your period may last for three to five days. Some last as long as seven days.

About Your Period
When It Will Start
Most girls have their first period around age 11. In most cases the first period is very mild — only a few drops of blood. For some young women, menstrual periods occur monthly on a regular cycle. Others periods may not be regular.

How to Keep Track
It is a good idea to use a calendar to keep track of your periods. Mark the first day your period starts on your calendar with an "X." Count the first "X" as day 1. Keep counting the days until you have your next period. If you do this every month, you'll be able to tell how many days there are between your periods.

When Your Period Hurts
Many women have mild cramps (dysmenorrhea) in the lower abdomen when their periods start. This is normal.

Some women also go through other changes in the days or weeks before their menstrual periods start. The most common symptoms are:

• Bloating
• Tender breasts
• Headache
• Feeling tired
• Mood swings
• Food cravings

To relieve your cramps and other symptoms, you can:

• Take over-the-counter pain relief, like aspirin, ibuprofen or acetaminophen
• Exercise regularly
• Reduce stress and try relaxation methods like deep breathing and yoga
• Place a heating pad or hot water bottle on your stomach
• Reduce sweets, salt and caffeine

Problems
Amenorrhea
Some women never start menstruating during their teenage years. Others who have had regular periods may stop having them. This is called amenorrhea.

The most common reason for a missed period is pregnancy. If you have had sex and miss a period, see your doctor right away.

See your doctor if you miss your periods often. A young woman should see her doctor if she has not started having periods by age 16 or if she has three months in a row without a period.

Heavy Bleeding
Some women have heavier bleeding than others. This can be normal. If your periods are heavier than usual or go on for longer than a week, they may not be normal.

Finally …

Menstruation is a normal, healthy process. In most cases it does not affect your day-to-day activities. If you have any concerns about your menstrual cycle, discuss them with your doctor.

This excerpt from ACOG's Patient Education Pamphlet is provided for your information. It is not medical advice and should not be relied upon as a substitute for visiting your doctor. If you need medical care, have any questions, or wish to receive the full text of this Patient Education Pamphlet, please contact your obstetrician-gynecologist.