Ovulation pain (mittelschmerz): causes, duration and when it is something else

It is important to separate the source from the strength of evidence. The figure 'over 40%' comes from a clinical review, not from a large population study with a uniform definition, so it is an approximation. Likewise, the description of the mechanism is the best available physiological explanation but has not been finally proven in studies that measured hormones, contractions and pain at the same time. In this article we therefore treat this information as clinically well established but of low strength in terms of scientific studies.

In a fertile cycle, under the influence of rising estradiol, the pituitary releases a sudden surge of luteinising hormone (LH), which triggers maturation of the egg and rupture of the Graafian follicle, that is ovulation. According to the StatPearls review, the pain coincides with the LH peak, before the follicle ruptures. Increased contractility of the smooth muscle in the ovarian wall around the follicle, dependent on prostaglandins, is pointed to as the probable cause. At the same time the authors note that simple stretching of the follicle wall by fluid is an unlikely explanation.

Further hypotheses appear in the literature: irritation of the peritoneum by a small amount of fluid or blood released when the follicle ruptures, and fallopian tube contractions. These are mechanistic proposals, not established facts. From a practical point of view, what matters is that the pain appears on the side of the ovary in which the dominant follicle is maturing and often changes side from cycle to cycle, but not always: in some women ovulation occurs repeatedly on the same side.

Typically ovulation pain lasts from a few minutes to a few hours, less often one to two days. If the pain is severe, persists for more than 2-3 days or builds up hour by hour, it is not the typical picture and another cause should be sought. Ovulation pain also should not recur in unchanged form through the whole luteal phase or precede the period by a week: such patterns more often point to other mechanisms, for example endometriosis, a functional cyst or premenstrual syndrome.

Mid-cycle pain is not always ovulatory. A 2023 review of the assessment of acute pelvic pain in women lists as urgent gynaecological causes ectopic pregnancy, ruptured ovarian cyst, adnexal torsion and pelvic inflammatory disease, and as urgent non-gynaecological causes appendicitis and pyelonephritis. Less urgent but common are sexually transmitted infections, pelvic floor myofascial pain, dysmenorrhoea and muscle strain.

The ACR imaging criteria for acute pelvic pain in women of reproductive age recommend a combination of transabdominal and transvaginal ultrasound with Doppler as the initial study, and CT of the abdomen and pelvis is considered when a non-gynaecological cause is suspected with a negative beta-hCG. For the reader the practical conclusion is simple: atypical mid-cycle pain is not a reason for guesswork on your own but for talking to a doctor and, usually, for an ultrasound.

After ovulation the corpus luteum forms from the ruptured follicle. Sometimes bleeding occurs inside it, a haemorrhagic cyst forms, and its rupture can cause bleeding into the peritoneal cavity (haemoperitoneum). A 2020 review describes that symptoms arise mainly from peritoneal irritation by blood, the differential diagnosis is broad and standard management has not been established. Bleeding from the corpus luteum is often self-limiting, so in stable patients watchful waiting with supportive treatment is used (analgesics, fluids, transfusion if needed), and surgical (laparoscopic) treatment is used when it is necessary.

In this context one case worth mentioning: in a report of a 27-year-old woman with type 1 von Willebrand disease, with a two-year history of severe ovulation pain from recurrent haemorrhagic cysts, mid-cycle tranexamic acid markedly reduced her symptoms. A single case report is no basis for using this drug in typical ovulation pain, but it shows that severe, recurrent ovulation pain in a woman with heavy periods or a tendency to bleed deserves investigation for a bleeding disorder.

Honestly: there is little evidence. We found no randomised trials comparing ways to relieve ovulation pain, and practical advice rests on clinical experience and on extrapolation from the treatment of other pelvic pains. For most women the pain is short and mild, so treatment is not needed, or warmth on the lower abdomen, rest and brief, occasional use of an over-the-counter analgesic, according to the leaflet and without contraindications (especially stomach or kidney disease, pregnancy and anticoagulant treatment), is enough.

It is worth noting that hormonal contraception is used to prevent haemorrhagic corpus luteum cysts in women with bleeding disorders and on anticoagulant treatment, as the review mentioned states, but it is not routine treatment of ordinary ovulation pain. If you are trying to plan a pregnancy, the presence of ovulation pain does not replace other methods of assessing ovulation.

At the visit the doctor will usually ask for a history, examine the abdomen and carry out a gynaecological examination, order a pregnancy test (if pregnancy is possible) and possibly a transvaginal ultrasound. If the pain is typical of mittelschmerz, the ultrasound may be normal or show a mature follicle or a small amount of fluid in the pouch of Douglas, which in itself is not abnormal and needs no treatment.

Ovulation pain is usually a harmless reminder that the cycle is working, but its mild nature should not lull vigilance. We recommend treating it as a diagnosis of exclusion: typical, short, one-sided mid-cycle pain without alarm symptoms can usually be observed and eased with simple methods, whereas any severe, atypical pain or pain with a late period needs prompt assessment, first of all a pregnancy test. To be frank, the scientific knowledge about mittelschmerz is modest, so it is wiser to base decisions on the general principles of assessing pelvic pain than on assurances that 'it is surely ovulation'.