What Causes Dysmenorrhea (Painful Menstrual Cramps)
Dysmenorrhea is caused by excessive prostaglandin production by the endometrium, leading to increased uterine contractility, vasoconstriction, uterine muscle ischemia, and hypoxia that results in pain. 1, 2, 3
Primary vs. Secondary Dysmenorrhea
The fundamental distinction determines the underlying mechanism:
Primary Dysmenorrhea
- Occurs in the absence of pelvic pathology and is purely a biochemical phenomenon 2, 3
- Results from hypersecretion of prostaglandins causing uterine hypercontractility, which produces ischemia and subsequent pain 1, 3, 4
- Typically presents in adolescence shortly after menarche 2, 5
- Pain is confined to the menstrual period (typically 1-3 days) and does not progressively worsen over years 5, 6
- Physical examination is normal 3, 5
- Affects 41-91.5% of reproductive-aged women 5
Secondary Dysmenorrhea
- Pain associated with underlying pelvic pathology such as endometriosis, adenomyosis, or uterine fibroids 1, 4, 5
- Characterized by progressive worsening of menstrual pain over time and pain extending beyond the menstrual period 6
- Endometriosis is the most common cause, affecting 2-10% of reproductive-aged women and presenting with secondary dysmenorrhea, deep dyspareunia, and sacral backache with menses 7, 6
- Approximately 50% of endometriosis patients present with associated infertility 6
- Uterine fibroids are the second most common cause of acute pelvic pain in perimenopausal/postmenopausal women, causing pain through torsion, prolapse, or acute degeneration 8
- Adenomyosis typically affects older, multiparous women and causes progressive dysmenorrhea 6, 4
Key Distinguishing Features
Red flags suggesting secondary dysmenorrhea requiring further evaluation:
- Progressive worsening of pain severity over months to years 6
- Pain timing extending beyond menstruation 6
- Associated infertility 6
- Abnormal physical examination findings 3
- Failure to respond to NSAIDs and hormonal contraceptives after 3-6 months 9
Clinical Implications
The diagnosis of primary dysmenorrhea is clinical and does not require imaging or laparoscopy in patients with typical symptoms and no risk factors for secondary causes 2, 3. However, transvaginal ultrasound is the recommended first-line imaging (sensitivity 82.5%, specificity 84.6%) when secondary causes need exclusion 6, 9.
A common pitfall is underdiagnosing and undertreating dysmenorrhea because women often accept it as a normal part of menstruation 2, 3. This leads to significant quality of life impairment, including school and work absenteeism 3, 5.