What causes pelvic pain during ovulation?

The cause of pelvic pain during ovulation, or "mittelschmerz" pain, is unknown. Some potential reasons for the discomfort include stretching of the surface of the ovary due to follicle growth before egg release, or the release of blood or fluid from the ruptured follicles, which can irritate the lining of the abdomen and cause pain.

Ovulation is the expulsion of a mature follicle containing an ovum or egg into the pelvic cavity. This usually occurs in the mid-cycle of a normal 28 day menstrual cycle. The release of this ovum or egg and its surrounding fluid causes what is named "Mittelschmerz" or mid cycle pain. The fluid can be irritating to the peritoneum enclosing the pelvic cavity. This thick oozing cyst fluid may cause tenderness and pain especially after it ruptures. The released ovum is then swept into the fallopian tube to be fertilized by the male sperm. If fertilization does not occur 14 days later in the cycle menstruation occurs.