Myths and Truths About the Menstrual Cycle

You may remember giggling and blushing throughout your health classes as your teacher explained the menstrual cycle. Well, for many of us that class took place a long time ago. As adults we need to brush up on the basic information we were given as teens.

The Basics

On average, the normal menstrual cycle is one in which a woman menstruates every 28 days, with ovulation occurring approximately 2 weeks after the onset of a woman's last period and 2 weeks prior to the onset of the next. However, normal is a relative term. Menstruation occurring every 25-36 days is still considered within the normal range.

There are several factors that can cause an irregular cycle, including younger age, stress, illness, or use of hormonal birth control methods.

A lot of women are confused about when during their cycles they can become pregnant. Trying to predict a time during your cycle when you can safely have sexual intercourse without fear of becoming pregnant can be all but impossible. The trickiest time is during ovulation. Although the egg lasts for only a day, sperm can last for up to 5 days. So, if you have had sex in the 5 days prior to or following ovulation, you could become pregnant.

It is also a fallacy that women cannot become pregnant if they have sex during their periods. For example, let's say your period lasts 7 days and sperm lasts 5 days. If your cycle is shorter than 28 days, you have the potential for pregnancy.

The amount of flow during a woman's period will depend on genetic factors, her overall health, the length of her cycle, and use of hormonal birth control. The amount of flow can vary from month to month, but on average blood loss is less than 3 ounces.

Sex Drive

For most women, the menstrual cycle and the hormones associated with it do not noticeably affect sex drive. Women not on hormonal methods of birth control may feel more interested in sex around the time they ovulate and some women may feel more sexual around the time of their periods, so sex drive is a very individual thing. It can be affected by such variables as a date, a bad day, illness, a new baby, or exhaustion. A partner's sex drive varies as well, it could also have an effect.

Sex drive may be greater during menopause because women may not be worried about pregnancy, their children have left home, and they may feel more sexual. Like their younger counterparts though, sex drive is variable and some women might experience a decrease after menopause.

Birth Control

Women may be confused about the effectiveness of the various methods of birth control. In theory, barrier methods of birth control such as the condom and diaphragm are effective in preventing pregnancy. In reality, however, the numbers show them to be less so. This may be because they must be readily available, and used correctly and consistently in order to be effective.

While oral birth control pills are more likely to be used correctly than barrier methods, women frequently forget to take it. If you use birth control pills and happen to miss a day, the information that comes with the prescription will give you directions to follow to protect yourself from unwanted pregnancy.

Toxic Shock

Toxic shock syndrome (TSS) is caused by toxins released by a bacteria present in the vaginal lining. When tampons are left in place for too long, the vaginal lining can dry out, allowing these toxins to enter the blood stream. Though rare, if left untreated, TSS can lead to kidney failure, respiratory failure, and death. Under very rare circumstances, diaphragms and sponges can also cause TSS. It is important to change your tampon every 4-8 hours, and not use one during the overnight hours. You may want to use pads instead of tampons at night.

When You Should See Your Healthcare Provider

Regular reproductive checkups are important for every woman. But should any of the following symptoms occur between scheduled checkups, see your healthcare provider:

  • Your period comes less than 25 days or more than 35 after the onset of your last period
  • Your period is frequently irregular
  • Your period lasts more than one week
  • Your flow is heavier than normal
  • There is more pain associated with your period than you consider to be normal
  • You experience pain during intercourse
  • Postmenopausal bleeding
  • You are of reproductive age and not having regular periods

You know your body best. Keep track of your normal cycle so you will know when something changes.


American Congress of Obstetricians and Gynecologists


The Society of Obstetricians and Gynaecologists of Canada
Women's Health Matters


Female reproductive endocrinology. Merck Manual Professional Version website. Available at:
...(Click grey area to select URL)
Updated August 2016. Accessed July 5, 2017.
Menstruation and the menstrual cycle fact sheet. Office on Women's Health website. Available at: Updated October 21, 2009. Accessed July 5, 2017.
Normal menstruation. Cleveland Clinic website. Available at:
...(Click grey area to select URL)
Accessed July 5, 2017.
Streptococcal toxic shock syndrome. EBSCO DynaMed Plus website. Available at: http://www.dynamed.... Updated March 20, 2017. Accessed July 5, 2017.
Last reviewed July 2017 by EBSCO Medical Review Board Michael Woods, MD, FAAP
Last Updated: 7/15/2015

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