What is the normal endometrial thickness in women?

Normal Endometrial Thickness

In postmenopausal women, normal endometrial thickness is ≤4 mm, which conveys a negative predictive value for endometrial cancer of nearly 100%. 1

Endometrial Thickness by Menopausal Status

Postmenopausal Women

• ≤4 mm is considered normal with a very high negative predictive value for malignancy 1
• 5 mm or greater warrants further evaluation, particularly in women with vaginal bleeding 1
• In asymptomatic postmenopausal women:
  • Mean endometrial thickness is approximately 2.3 mm (range 0-10 mm) 2
  • Endometrial thickness correlates with body weight and BMI 2
  • A threshold of 11 mm is suggested for consideration of biopsy in women without vaginal bleeding 3

Premenopausal Women

• Normal endometrial thickness varies throughout the menstrual cycle
• Early proliferative phase: 4-7 mm
• Late proliferative/ovulatory phase: 7-11 mm
• Secretory phase: 7-14 mm

Clinical Implications of Endometrial Thickness

When to Evaluate Further

• Postmenopausal women with ANY abnormal vaginal bleeding should be evaluated regardless of endometrial thickness 1
• Endometrial thickness ≥5 mm in postmenopausal women generally prompts evaluation by endometrial tissue sampling 1
• Endometrial thickness ≥11 mm in asymptomatic postmenopausal women is an indication for endometrial biopsy 1, 3

Risk Stratification

• The risk of endometrial cancer in postmenopausal women with vaginal bleeding:
  • Approximately 7.3% if endometrium is >5 mm
  • <0.07% if endometrium is ≤5 mm 3
• The risk of endometrial cancer in postmenopausal women WITHOUT vaginal bleeding:
  • Approximately 6.7% if endometrium is >11 mm
  • 0.002% if endometrium is ≤11 mm 3
• Risk increases with age: at 11 mm threshold, cancer risk rises from 4.1% at age 50 to 9.3% at age 79 3

Factors Affecting Endometrial Thickness

• Body weight and BMI: Higher BMI correlates with greater endometrial thickness 2
• Hormone replacement therapy: Affects endometrial thickness measurements 4
  • Women on unopposed estrogen may have thicker endometrium
  • Women on combined estrogen-progestogen therapy may have variable thickness
• Age: Older postmenopausal women tend to have thinner endometrium

Diagnostic Approach

• Transvaginal ultrasound (TVUS) is the first-line screening test for evaluating endometrial thickness 1
• For abnormal thickness or persistent symptoms, endometrial sampling is recommended:
  • Pipelle device has 99.6% sensitivity for detecting endometrial carcinoma 1
  • Vabra device has 97.1% sensitivity 1
• Hysteroscopy with directed biopsy is superior to blind sampling techniques for focal lesions 1

Common Pitfalls to Avoid

• Do not ignore vaginal bleeding in postmenopausal women, regardless of endometrial thickness 1
• Do not rely solely on endometrial thickness in women on hormone replacement therapy without considering the type of hormone regimen 4
• Remember that endometrial thickness measurements should be double-layer (anterior and posterior walls together)
• Consider that endometrial volume measurements may be superior to thickness measurements for cancer detection in some cases 5