Menstrual Cramps (cont.)

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Why are some cramps so painful?

Menstrual cramps are caused by the uterine contractions that occur in response to prostaglandins and other chemicals. The cramping sensation is intensified when clots or pieces of bloody tissue from the lining of the uterus pass through the cervix, especially if a woman's cervical canal is narrow.

The difference between menstrual cramps that are more painful and those that are less painful may be related to a woman's prostaglandin levels. Women with menstrual cramps have elevated levels of prostaglandins in the endometrium (uterine lining) when compared with women who do not experience cramps. Menstrual cramps are very similar to those a pregnant woman experiences when she is given prostaglandin as a medication to induce labor.

Can menstrual cramps be measured?

Yes, but measuring the strength of menstrual cramps is not routinely done in clinical practice. Researchers have demonstrated that menstrual cramps can be scientifically documented by measuring the pressure within the uterus and the number and frequency of uterine contractions. During a normal menstrual period, the average woman has contractions of a low pressure (50-80 mm Hg), which last 15-30 seconds at a frequency of 1-4 contractions every 10 minutes. When a woman with dysmonorrhea has menstrual cramps, her contractions are of a higher pressure (they may exceed 400 mm Hg), last longer than 90 seconds, and often occur less than 15 seconds apart.

What other factors influence menstrual cramps?

  • As mentioned above, an unusually narrow cervical canal tends to increase menstrual cramps.
  • Another anatomical factor thought to contribute to menstrual cramps is a backwards tilting of the uterus (a retroverted uterus).
  • Lack of exercise is now recognized to contribute to painful menstrual cramps, because exercise releases endorphins that relieve pain.
  • It has long been thought that psychological factors also play a role. For example, it is widely accepted that emotional stress can increase the discomfort of menstrual cramps.
  • Adenomyosis and endometriosis can increase the severity of menstrual cramps
  • Having uterine fibroids can worsen menstrual cramping
Medically Reviewed by a Doctor on 3/31/2014

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