What is the normal endometrial thickness in women?

Normal Endometrial Thickness in Women

Normal endometrial thickness is ≤4 mm in postmenopausal women and varies by menstrual cycle phase in premenopausal women. 1

Endometrial Thickness by Menopausal Status

Postmenopausal Women

• An endometrial thickness ≤4 mm in postmenopausal women conveys a negative predictive value for endometrial cancer of nearly 100% 1
• Endometrial thickness ≥5 mm in postmenopausal women generally prompts evaluation by endometrial tissue sampling, particularly in the presence of vaginal bleeding 1
• In asymptomatic postmenopausal women (without vaginal bleeding), a higher threshold of >11 mm may be more appropriate for recommending biopsy 2
• Body weight correlates with endometrial thickness in postmenopausal women with measurements <5 mm 3

Premenopausal Women

• Endometrial thickness varies throughout the menstrual cycle:
  • Early proliferative phase: 4-7 mm
  • Late proliferative phase: 7-11 mm
  • Secretory phase: 7-14 mm

Clinical Implications

When to Investigate Endometrial Thickness

• Postmenopausal women with any abnormal vaginal bleeding should be evaluated regardless of endometrial thickness 1
• Endometrial thickness ≥5 mm in postmenopausal women with bleeding requires tissue sampling 1
• Endometrial thickness ≥11 mm in asymptomatic postmenopausal women warrants consideration of biopsy (risk of cancer approximately 6.7%) 2
• Endometrial thickness ≥11 mm in asymptomatic postmenopausal women carries increasing risk with age (from 4.1% at age 50 to 9.3% at age 79) 2

Hormone Replacement Therapy Effects

• Hormone replacement therapy increases endometrial thickness 4
• Different evaluation thresholds may apply based on hormone status:
  • Women receiving unopposed estrogen or continuous estrogen and progestogen with thickness 0.8-1.5 cm should undergo biopsy 4
  • Any patient with endometrial thickness ≥1.5 cm should undergo histologic diagnosis regardless of hormone status 4

Diagnostic Considerations

• Transvaginal ultrasound (TVUS) is the first-line screening test for evaluating endometrial thickness 1
• Three-dimensional ultrasound measurements of endometrial volume may be superior to thickness measurements for detecting endometrial cancer in symptomatic women 5
• Endometrial sampling devices like Pipelle (99.6% sensitivity) and Vabra (97.1% sensitivity) are highly effective for detecting endometrial carcinoma 1

Common Pitfalls

• Failing to evaluate postmenopausal women with vaginal bleeding regardless of endometrial thickness
• Using the same endometrial thickness threshold for symptomatic and asymptomatic postmenopausal women
• Not accounting for hormone replacement therapy when interpreting endometrial thickness
• Not considering patient's age and body weight, which can influence normal endometrial thickness values