Cramping that occurs when a woman is not on her period can be attributed to ovulation, as stated by WebMD. When the body releases an egg, it can cause cramps on one side of the belly. These cramps are known as mittelschmerz and occur around the midpoint of a woman's menstrual cycle.
Another common cause of cramping other than a period is early pregnancy, as reported by the American Pregnancy Association. The cramping occurs as the fertilized egg implants and burrows into the uterus.
If a woman experiences severe cramping and there is a possibility she might be pregnant, she should contact her doctor, as violent cramping may be a sign of an ectopic pregnancy.