As of 2015, the exact cause of pain during ovulation, or mittelschmerz, is unknown, according to WebMD. However, researchers theorize that blood and excess bodily fluids may irritate the lining of a woman's abdominal cavity, causing pain.
As an egg is developing in the ovaries, it is surrounded by follicular fluid, states WebMD. During ovulation, when the egg is released, this fluid and some blood are released along with it. When those two fluids reach the abdominal cavity, they may cause irritation and, consequently, pain. Usually, pain goes away once the body has absorbed the blood and the follicular fluid, which could be anywhere from a few minutes to several hours.
Pain during ovulation can range from mild to severe, states WebMD. It is generally felt on one side of the abdomen, but the exact position can vary from month to month. In some cases, mittelschmerz is accompanied by vaginal bleeding. Some women also experience nausea while suffering from mittelschmerz, especially if the pain is severe.
The timing of each painful occurrence can simplify the diagnosing of mittelschmerz, as ovulation usually starts two weeks after a woman's menstrual period, according to WebMD. Abdominal pain that occurs during this time could be mittelschmerz. To be sure, a doctor may ask a woman to chart her menstrual cycles. He may also perform abdominal and pelvic exams to rule out other conditions before a diagnosis is made.