What are cramps?
When the lining of the uterus sheds, it has to pass through the cervixso it can leave the body. The uterus contracts (squeezes) to do this, pushingthe menstrual fluid out. When these contractions become painful we callthem cramps. Not all women have cramps. It is common for girls who havejust started their periods to have no pain, for instance. Women who havehad babies, too, often report that even though they used to get cramps,they no longer do. But most women experience at least a little discomfortduring their periods sometime or another.
Cramps tend to come with heavy bleeding, so they usually only last forthe first day or two of your period, when there is the most bleeding. Sometimesthey will begin before you start bleeding.
What do they feel like?
Cramps can be different in each woman.
They might be just tiny aches and twinges in her lower belly which arehardly noticeable. Or she might feel like a big hand is in her belly, squeezinghard. Or she might feel strange shooting pains that go up the insides ofher thighs. Her lower back might hurt. Or she might just feel a certainkind of fullness inside - like a pressure that needs to be released.
Why do cramps hurt?
I don't know. I don't think anyone knows for sure. We know cramps areusually come with heavy bleeding and the contractions (squeezing motions)of the uterus that cause this bleeding. The contractions should not haveto hurt, however. Your intestines, for instance, contract to move foodthrough them when you are digesting, and you usually cannot feel thosecontractions.
One theory is that cramps might be caused by having too much prostaglandinin your system. Prostaglandins are chemicals made by your body to helpit do different things. Certain types of prostaglandin make your uteruscontract.
But if there is too much prostaglandin being produced, the contractionsof the uterus, which are supposed to be painless, become very strong andlast longer than they should. As a result, oxygen can't get to the tightenedmuscles, and we feel this lack of oxygen as cramping (the same thing thathappens when you get cramps from running).
The prostaglandin can also leak through the walls of your intestinesand cause diarrhea, which some women get when they have cramps.
Isn't that nice to know?
( Note: severe cramping can be a symptom of a chronic disease called endometriosis)