Cause of cramps will be according to site of origin. But in an usual scenario, cramps in women usually occur during menstruation, pregnancy, lactation period etc. Levels of prostaglandin increases during menstruation which is responsible for cramps during menstruation. During pregnancy - stretching of round ligament, gaseous distention of gut, constipation, nutritional deficiency (Calcium, magnesium), decreasing of venous return by compression of great vessel by growing baby within the uterus (causes leg cramps) etc are the cause of cramps. During lactation period nutritional deficiency of calcium causes cramps. You can know more about pregnancy cramps here - http://hubpages.com/health/All-about-pregnancy-cra... .