What are menstrual cramps? What causes menstrual cramps?

What are menstrual cramps?
Menstrual cramps are pains in the abdominal (belly) and pelvic areas that are experienced by a woman as a result of her menstrual period. Menstrual cramps are not the same as the discomfort felt during premenstrual syndrome (PMS), although the symptoms of both disorders can sometimes be experienced as a continual process. Many women suffer from both PMS and menstrual cramps.

Menstrual cramps can range from mild to quite severe. Mild menstrual cramps may be barely noticeable and of short duration - sometimes felt just as a sense of light heaviness in the belly. Severe menstrual cramps can be so painful that they interfere with a woman's regular activities for several days.

What causes menstrual cramps?

Each month, the inner lining of the uterus (the endometrium) builds up in preparation for a possible pregnancy. After ovulation, if the egg is not fertilized by a sperm, no pregnancy will result and the current lining of the uterus is no longer needed. The woman's estrogen and progesterone hormone levels decline, and the lining of the uterus becomes swollen and dies. It is then shed and will be replaced by a new lining in the next monthly cycle.

When the old uterine lining begins to break down, molecular compounds called prostaglandins are released. These compounds cause the muscles of the uterus to contract. When the uterine muscles contract, they constrict the blood supply (vasoconstriction) to the endometrium. This contraction blocks the delivery of oxygen to the tissue of the endometrium which, in turn, breaks down and dies. After the death of this tissue, the uterine contractions literally squeeze the old endometrial tissue through the cervix and out of the body by way of the vagina. Other substances known as leukotrienes, which are chemicals that play a role in the inflammatory response, are also elevated at this time and may be related to the development of menstrual cramps.