Introduction to primary dysmenorrhoea

Dysmenorrhoea (painful menstrual bleeding) is one of the most common gynaecological problems, affecting 50 to 90% of individuals who have menstrual cycles. It is classified as primary (if it results from physiological changes during a menstrual period) or secondary (if caused by a disorder of the reproductive system). Some may not be aware that dysmenorrhoea is abnormal and warrants investigation and treatment.

Risk factors for primary dysmenorrhoea include early onset of menarche and long duration of menstrual bleeding. Period pain that starts within 6 to 12 months of menarche is a strong diagnostic indicator of primary dysmenorrhoea; diagnosis in this age group can generally be made on history alone.

The approach to the initial history and examination is as for heavy menstrual bleeding. Diagnosis of primary dysmenorrhoea requires exclusion of secondary causes such as endometriosis, pelvic inflammatory disease, fibroids, adenomyosis, endometrial polyps, intrauterine devices and congenital abnormalities. Aspects of the medical history that suggest dysmenorrhoea is secondary include:

  • onset of dysmenorrhoea in the third decade or later (although it may be from the onset of menstruation)
  • a change in the pattern of period pain
  • the presence of dyspareunia, heavy menstrual bleeding, intermenstrual bleeding or postcoital bleeding
  • irregular periods
  • a poor response to a 3-month trial of treatment
  • other symptoms of endometriosis
  • family history of endometriosis.

Ultrasound is required if secondary dysmenorrhoea is suspected. A transvaginal scan is preferred because it is gives better detail; a transabdominal scan is an alternative if a transvaginal scan is not available or is declined. Scans in adolescents can be useful to exclude uterine structural abnormalities. An incidental finding of polycystic morphology in the ovaries is common in adolescents and does not routinely require investigation; normal adolescent ovaries may have a polycystic appearance for up to 8 years after menarche.

Note: Normal adolescent ovaries may have a polycystic appearance for up to 8 years after menarche and do not routinely require investigation.

Treatment of secondary dysmenorrhoea is directed to its cause; see Endometriosis, Heavy menstrual bleeding and Pelvic inflammatory disease.