Merck Manual

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JoAnn V. Pinkerton

, MD, University of Virginia Health System

Last full review/revision Dec 2020
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Dysmenorrhea is uterine pain around the time of menses. Pain may occur with menses or precede menses by 1 to 3 days. Pain tends to peak 24 hours after onset of menses and subside after 2 to 3 days. It is usually sharp but may be cramping, throbbing, or a dull, constant ache; it may radiate to the legs.

Headache, nausea, constipation or diarrhea, lower back pain, and urinary frequency are common; vomiting occurs occasionally.

Symptoms of premenstrual syndrome may occur during part or all of menses.

Sometimes endometrial clots or casts are expelled.

Etiology of Dysmenorrhea

Dysmenorrhea can be

  • Primary (more common)

  • Secondary (due to pelvic abnormalities)

Primary dysmenorrhea

Symptoms of primary dysmenorrhea cannot be explained by structural gynecologic disorders. Pain is thought to result from uterine contractions and ischemia, probably mediated by prostaglandins (eg, prostaglandin F2-alpha, a potent myometrial stimulant and vasoconstrictor) and other inflammatory mediators produced in secretory endometrium and possibly associated with prolonged uterine contractions and decreased blood flow to the myometrium.

Contributing factors may include the following:

  • Passage of menstrual tissue through the cervix

  • High levels of prostaglandin F2-alpha in menstrual fluid

  • A narrow cervical os

  • A malpositioned uterus

  • Lack of exercise

  • Anxiety about menses

Primary dysmenorrhea begins within a year after menarche and occurs almost invariably in ovulatory cycles. The pain usually begins when menses start (or just before) and persists for the first 1 to 2 days; this pain, described as spasmodic, is superimposed over constant lower abdominal pain, which may radiate to the back or thigh. Patients may also have malaise, fatigue, nausea, vomiting, diarrhea, low back pain, or headache.

Risk factors for severe symptoms include the following:

  • Early age at menarche

  • Long or heavy menstrual periods

  • Smoking

  • A family history of dysmenorrhea

Symptoms tend to lessen with age and after pregnancy.

In about 5 to 15% of women with primary dysmenorrhea, cramps are severe enough to interfere with daily activities and may result in absence from school or work.

Secondary dysmenorrhea

Symptoms of secondary dysmenorrhea are due to pelvic abnormalities. Almost any abnormality or process that can affect the pelvic viscera can cause dysmenorrhea.

Common causes of secondary dysmenorrhea include

In a few women, pain occurs when the uterus attempts to expel tissue through an extremely tight cervical os (secondary to conization, loop electrosurgical excision procedure [LEEP], cryocautery, or thermocautery). Pain occasionally results from a pedunculated submucosal fibroid or an endometrial polyp protruding through the cervix.

Risk factors for severe secondary dysmenorrhea are the same as those for primary.

Secondary dysmenorrhea usually begins during adulthood unless caused by congenital malformations.

Evaluation of Dysmenorrhea

Clinicians can identify dysmenorrhea based on symptoms. They then determine whether dysmenorrhea is primary or secondary.


History of present illness should cover complete menstrual history, including age at onset of menses, duration and amount of flow, time between menses, variability of timing, and relation of menses to symptoms.

Clinicians should also ask about

  • The age at which symptoms began

  • Their nature and severity

  • Factors that relieve or worsen symptoms (including the effects of contraceptives)

  • Degree of disruption of daily life

  • Effect on sexual activity

  • Presence of pelvic pain unrelated to menses

  • Response to acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs)

Review of systems should include accompanying symptoms such as cyclic nausea, vomiting, bloating, diarrhea, and fatigue.

Past medical history should identify known causes, including endometriosis, uterine adenomyosis, or fibroids. Method of contraception should be ascertained, specifically asking about IUD use.

Past surgical history should identify procedures that increase risk of dysmenorrhea, such as cervical conization and endometrial ablation.

Sexual history should include prior or current history of sexual abuse or other traumatic events.

Physical examination

Pelvic examination focuses on detecting causes of secondary dysmenorrhea. The vagina, vulva, and cervix are inspected for lesions and for masses protruding through the cervical os. Structures are palpated to check for a tight cervical os, prolapsed polyp or fibroid, uterine masses, adnexal masses, thickening of the rectovaginal septum, induration of the cul-de-sac, and nodularity of the uterosacral ligament.

The abdomen is examined for evidence of peritonitis.

Red flags

The following findings are of particular concern:

  • New or sudden-onset pain

  • Unremitting pain

  • Fever

  • Vaginal discharge

  • Evidence of peritonitis

Interpretation of findings

Red flag findings suggest a cause of pelvic pain other than dysmenorrhea.

Primary dysmenorrhea is suspected if

  • Symptoms begin soon after menarche or during adolescence.

Secondary dysmenorrhea is suspected if

  • Symptoms begin after adolescence.

  • Patients have known causes, including uterine adenomyosis, fibroids, a tight cervical os, a mass protruding from the cervical os, or, particularly, endometriosis.

Endometriosis is considered in patients with adnexal masses, thickening of the rectovaginal septum, induration of the cul-de-sac, nodularity of the uterosacral ligament, or, occasionally, nonspecific vaginal, vulvar, or cervical lesions.


Testing aims to exclude structural gynecologic disorders. Most patients should have

  • Pregnancy testing

  • Pelvic ultrasonography

Intrauterine and ectopic pregnancy are ruled out by pregnancy testing. If pelvic inflammatory disease is suspected, cervical cultures are done.

Pelvic ultrasonography is highly sensitive for pelvic masses (eg, ovarian cysts, fibroids, endometriosis, uterine adenomyosis) and can locate lost and abnormally located IUDs.

If these tests are inconclusive and symptoms persist, other tests are done, such as the following:

  • Hysterosalpingography or sonohysterography to identify endometrial polyps, submucous fibroids, or congenital abnormalities

  • MRI to identify other abnormalities, including congenital abnormalities, or, if surgery is planned, to further define previously identified abnormalities

  • IV pyelography, but only if a uterine malformation has been identified as causing or contributing to the dysmenorrhea

If results of all other tests are inconclusive, hysteroscopy or laparoscopy can be done. Laparoscopy is the most definitive test because it enables clinicians to directly examine all of the pelvis and reproductive organs and to check for abnormalities.

Treatment of Dysmenorrhea

Underlying disorders are treated.

General measures

Symptomatic treatment of dysmenorrhea begins with adequate rest and sleep and regular exercise. A low-fat diet and nutritional supplements, such as omega-3 fatty acids, flaxseed, magnesium, vitamin B1, vitamin E, and zinc, are suggested as potentially effective.

Women with primary dysmenorrhea are reassured about the absence of structural gynecologic disorders.


If pain persists, NSAIDs (which relieve pain and inhibit prostaglandins) are typically tried. NSAIDs are usually started 24 to 48 hours before and continued until 1 or 2 days after menses begin.

If the NSAID is ineffective, suppression of ovulation with a low-dose estrogen/progestin oral contraceptive may be tried.

Other hormone therapy, such as danazol, progestins (eg, levonorgestrel, etonogestrel, depot medroxyprogesterone acetate), gonadotropin-releasing hormone agonists, or a levonorgestrel-releasing IUD, may decrease dysmenorrheal symptoms.

Periodic adjunctive use of analgesics may be needed.

Other treatments

Hypnosis is being evaluated as treatment. Other proposed nondrug therapies, including acupuncture, acupressure, chiropractic therapy, and transcutaneous electrical nerve stimulation, have not been well-studied but may benefit some patients.

For intractable pain of unknown origin, laparoscopic presacral neurectomy or uterosacral nerve ablation has been efficacious in some patients for as long as 12 months.

Key Points

  • Most dysmenorrhea is primary.

  • Check for underlying structural pelvic lesions.

  • Usually, before doing other tests, do ultrasonography to check for structural gynecologic disorders.

  • An NSAID or an NSAID plus a low-dose oral contraceptive is usually effective.

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