Why may an intrauterine device (IUD) not control abnormal uterine bleeding (AUB)?

Why an IUD May Not Control Abnormal Uterine Bleeding

An IUD may fail to control abnormal uterine bleeding due to structural uterine abnormalities (particularly fibroids distorting the cavity), device expulsion, underlying pathology such as malignancy or infection, or simply because copper IUDs worsen rather than improve bleeding patterns.

Type of IUD Matters Critically

The type of IUD fundamentally determines its effect on bleeding:

• Copper IUDs (Cu-IUD) typically worsen bleeding and are contraindicated for heavy menstrual bleeding management, as they can intensify dysmenorrhea and increase menstrual blood loss 1
• Levonorgestrel-releasing IUDs (LNG-IUD) are therapeutic for abnormal uterine bleeding in most cases, with evidence showing beneficial effects in treating menorrhagia 1
• If a copper IUD was placed for contraception in someone with pre-existing heavy bleeding, it will predictably fail to control and likely worsen the bleeding 1

Structural Causes of LNG-IUD Failure

Even when the appropriate LNG-IUD is used, anatomical factors can prevent effectiveness:

Uterine Fibroids

• LNG-IUD efficacy drops significantly to only 55.6% in women with leiomyomas, compared to 88.7% for adenomyosis and 95.5% for endometrial hyperplasia 2
• Expulsion rates are substantially higher with fibroids (11%) versus without fibroids (0-3%), though some studies showed rates up to 20% 1
• Women with fibroids and heavy bleeding are more likely to require surgical intervention despite LNG-IUD placement 2

Cavity Distortion

• Any congenital or acquired uterine abnormality that distorts the cavity is incompatible with IUD function and represents a Category 4 contraindication (should not be used) 1
• Anatomic distortion prevents proper IUD placement and positioning, rendering it ineffective 1

Device Malposition or Expulsion

• IUD displacement is a primary reason for treatment failure and must be ruled out when bleeding persists 3
• Proper placement should be verified by checking for IUD strings 3
• Partial expulsion allows continued bleeding while providing inadequate endometrial suppression

Undiagnosed Underlying Pathology

The CDC guidelines emphasize that unexplained vaginal bleeding with suspicion for serious conditions is a Category 4 contraindication for IUD initiation until evaluated 1:

• Endometrial or cervical malignancy can present as persistent bleeding that an IUD cannot control 1
• Active pelvic inflammatory disease or STIs at the time of insertion can cause ongoing bleeding 1
• Pregnancy complications including ectopic pregnancy must be excluded 3
• Coagulopathies or bleeding disorders may overwhelm the IUD's hemostatic effects 4

Timing and Expectations

• Unscheduled spotting or light bleeding is expected during the first 3-6 months of LNG-IUD use and does not represent treatment failure 3, 5
• Treatment should only be considered unsuccessful if bleeding persists beyond this 6-month adjustment period 3
• By 2 years, approximately half of LNG-IUD users achieve amenorrhea or oligomenorrhea 5

Common Pitfall: Premature Assessment

A critical error is judging LNG-IUD effectiveness too early. The device requires 3-6 months to achieve maximal endometrial suppression 3, 5. During this period, irregular bleeding is normal and should be managed with NSAIDs for 5-7 days or short courses of combined oral contraceptives (10-20 days) rather than removing the device 3.

When to Suspect True Failure

Consider the LNG-IUD genuinely ineffective when:

• Bleeding persists or worsens beyond 6 months despite medical management 3
• Imaging reveals large submucous fibroids or cavity distortion 2, 6
• Device strings are not visible, suggesting expulsion 3
• Underlying pathology is identified that warrants removal 3