Mittelschmerz is one-sided lower-abdominal pain that occurs in women at or around the time of ovulation.

About 20% of women experience mittelschmerz, or pain associated with ovulation. The pain may occur just before, during, or after ovulation.

There are several explanations for the cause of this pain. Just prior to ovulation, follicle growth may stretch the surface of the ovary, causing pain. At the time of ovulation, fluid or blood is released from the ruptured egg follicle and may cause irritation of the abdominal lining. Mittelschmerz may be felt on one side one month, then switch to the opposite side the next month, or it may be felt on the same side for several months in succession.

The pain is not harmful and does not signify the presence of disease. In fact, women who feel this pain may be at an advantage when planning or trying to avoid pregnancy. A woman is most likely to become pregnant just before ovulation, on the day of ovulation, or immediately after ovulation. However, birth control methods that rely solely on predicting ovulation are far from completely reliable.

Lower-abdominal pain that is:

• One-sided
• Recurrent or with similar pain in past
• Typically lasting minutes to a few hours, but may extend as long as 24-48 hours
• Usually sharp, cramping, distinctive pain
• Severe (rare)
• May switch sides from month to month or from one episode to another
• Begins midway through the menstrual cycle

A pelvic examination shows no abnormalities. Other diagnostic procedures (such as an abdominal ultrasound) may be performed to rule out other causes of ovarian pain if ovulatory pain is prolonged.

No treatment is usually necessary. Pain relievers (analgesics) may be needed in cases of prolonged or intense pain.

The outcome is expected to be excellent.

There are usually no complications.

Call for an appointment with your health care provider if midcycle ovulation pain seems to change or become unusually prolonged.

Hormonal forms of contraception can be taken to prevent ovulation -- and therefore ovulatory pain -- but otherwise there is no known prevention.

Goldman L, Ausiello D. Cecil Textbook of Medicine, 22nd ed. Philadelphia, Pa: WB Saunders; 2004:1495.

Rakel RE. Textbook of Family Practice. 6th ed. Philadelphia, Pa: WB Saunders; 2002:679.