On which day of the menstrual cycle should an endometrial biopsy be performed for abnormal uterine bleeding (AUB)?

Timing of Endometrial Biopsy for Abnormal Uterine Bleeding

Endometrial biopsy for abnormal uterine bleeding should be performed immediately after menstrual bleeding has ceased to obtain the most accurate and reliable sample.

Rationale for Timing

The timing of endometrial biopsy is crucial for accurate diagnosis in patients with abnormal uterine bleeding (AUB). Evidence supports performing the biopsy at specific points in the menstrual cycle:

• Immediately after menstrual bleeding has ceased (early follicular phase) is optimal as it provides:
  • The thinnest endometrial lining (mean 4.3±1.2 mm at day 7 of cycle) 1
  • Better visualization and access to the endometrial cavity
  • Reduced risk of procedure-related bleeding
  • More reliable histological interpretation

Procedural Considerations

When performing an endometrial biopsy for AUB:

• Use an endometrial biopsy catheter inserted through the cervix into the uterine cavity 2
• Create suction by drawing out the catheter's piston
• Sample tissue by rolling the catheter while moving it in and out of the uterine cavity 2
• Consider pain management:
  • NSAIDs administered orally before the procedure
  • Topical lidocaine applied to the cervix 2
  • Avoid unnecessary use of tenaculum as it increases pain 2

Clinical Decision Algorithm

1. For premenopausal women with AUB:

   • Schedule biopsy immediately after cessation of menstrual bleeding
   • Biopsy is indicated for women with risk factors for endometrial cancer or those with persistent AUB despite medical therapy 3

2. For perimenopausal women with AUB:

   • Endometrial sampling is essential, particularly in women over 45 who are at higher risk of endometrial pathology 4
   • Schedule biopsy early in the cycle (after bleeding stops)

3. For postmenopausal women with AUB:

   • Immediate endometrial sampling is required regardless of cycle day
   • Endometrial biopsy is highly specific for diagnosing atypical hyperplasia and endometrial cancer in this population 2

Important Considerations

• If transvaginal ultrasound shows endometrial thickness ≥5 mm in postmenopausal women, endometrial sampling is recommended 5
• In premenopausal women, endometrial thickness varies with cycle phase and is not a reliable indicator of pathology 5
• Consider hysteroscopy with directed biopsy if:
  • Initial blind biopsy is insufficient
  • Focal lesions are suspected
  • Persistent or recurrent symptoms occur despite normal biopsy results 2, 6

Pitfalls to Avoid

• Performing biopsy during active bleeding (reduces sample quality)
• Relying solely on blind sampling in postmenopausal women (may miss focal lesions) 2
• Failing to obtain adequate tissue sample (requires further evaluation) 2
• Not recognizing that pregnancy is the only absolute contraindication to the procedure 2
• Neglecting follow-up when symptoms persist despite normal biopsy results 2

By performing endometrial biopsy immediately after menstrual bleeding has ceased, clinicians can optimize diagnostic accuracy while minimizing patient discomfort and procedural complications.