Normal Menstrual Cycle
Topic Overview
What is a menstrual cycle?
The menstrual cycle is the series of changes a woman's body goes through to prepare for a pregnancy. About once a month, the uterus grows a new lining (endometrium) to get ready for a fertilized egg
. When there is no fertilized egg to start a pregnancy, the uterus sheds its lining. This is the monthly menstrual bleeding
The menstrual cycle is from Day 1 of bleeding to Day 1 of the next time of bleeding. Although the average cycle is 28 days, it is perfectly normal to have a cycle that is as short as 21 days or as long as 35 days.1 For a teen, a normal cycle can last up to 45 days.2
Girls usually start having menstrual periods between the ages of 11 and 14. Women usually start to have fewer periods between ages 39 and 51. Women in their 40s and teens may have cycles that are longer or change a lot. If you are a teen, your cycles should even out with time. If you are nearing menopause, your cycles will probably get longer and then will stop.
Talk to your doctor if you notice any big change in your cycle. It’s especially important to check with your doctor if you have three or more cycles that last longer than 7 days or are very heavy. Also call if you have bleeding between your periods or pelvic pain that is not from your period.
What controls the menstrual cycle?
Your hormones control your menstrual cycle. During each cycle, your brain's hypothalamus and pituitary gland send hormone signals back and forth with your ovaries. These signals get the ovaries and uterus ready for a pregnancy.
The hormones estrogen and progesterone play the biggest roles in how the uterus changes during each cycle.
- Estrogen builds up the lining of the uterus.
- Progesterone increases after an ovary releases an egg (ovulation) at the middle of the cycle. This helps the estrogen keep the lining thick and ready for a fertilized egg.
- A drop in progesterone (along with estrogen) causes the lining to break down. This is when your period starts.
A change in hormone levels can affect your cycle or fertility. For example, teens tend to have low or changing progesterone levels. This is also true for women close to menopause. That is why teens and women in their 40s may have heavy menstrual bleeding and cycles that change in length.
Other things can change your cycle. They include birth control pills, low body fat, losing a lot of weight, or being overweight. Stress or very hard exercise also can change your cycle. Pregnancy is the most common cause of a missed period.
What common symptoms are linked to the menstrual cycle?
Some women have no pain or other problems. But other women have symptoms before and during their period.
For about a week before a period, many women have some premenstrual symptoms. You may feel more tense or angry. You may gain water weight and feel bloated. Your breasts may feel tender. You may get acne. You also may have less energy than usual. A day or two before your period, you may start having pain (cramps) in your belly, back, or legs. These symptoms go away during the first days of a period.
When your ovary releases an egg in the middle of your cycle, you may have pain in your lower belly. You also might have red spotting for less than a day. Both are normal.
How can women take care of bleeding and symptoms?
You can use pads or tampons to manage bleeding. Whichever you use, be sure to change the pad or tampon at least every 4 to 6 hours during the day. Pads may be best at night.
Many women can improve their symptoms by getting regular exercise and eating a healthy diet. It also may help to limit alcohol and caffeine. Try to reduce stress.
A heating pad, hot water bottle, or warm bath also can help with cramps. You can take an over-the-counter medicine such as ibuprofen or naproxen before and during your period to reduce pain and bleeding. 3, 4
Frequently Asked Questions
Learning about the menstrual cycle:
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| Author: | Shannon Erstad, MBA/MPH Marianne Flagg | Last Updated: April 3, 2007 |
| Medical Review: | Kathleen Romito, MD - Family Medicine Kirtly Jones, MD - Obstetrics and Gynecology | |
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