Is 0.31 cm (3.1 mm) Endometrium Normal?
Yes, an endometrial thickness of 3.1 mm is normal and reassuring in a postmenopausal woman without bleeding, with a negative predictive value for endometrial cancer approaching 100%. 1, 2
Clinical Context and Interpretation
In postmenopausal women without abnormal uterine bleeding, an endometrial thickness <4 mm effectively excludes endometrial malignancy. 1, 2 Your measurement of 3.1 mm falls well below this threshold and is considered atrophic endometrium, which is the expected finding in postmenopausal women. 3
Key Thresholds by Clinical Scenario
Postmenopausal women WITH bleeding: Endometrial thickness ≤4-5 mm has a negative predictive value for cancer of nearly 100% 1, 3, 4
Postmenopausal women WITHOUT bleeding: The threshold for concern is significantly higher at 11 mm, as the baseline cancer risk is much lower in asymptomatic women 5
Your measurement of 3.1 mm: This is below both thresholds and represents normal atrophic endometrium 6, 3
What This Means for Management
No immediate intervention is needed with an endometrial thickness of 3.1 mm in an asymptomatic postmenopausal woman. 2 The American College of Radiology confirms that measurements at this level are reassuring regardless of other factors such as estrogen levels. 2
Important Caveats
Endometrial thickness alone is not sufficient—the ultrasound report must also comment on endometrial appearance and texture. 2 Abnormal echogenicity or heterogeneous texture can indicate pathology even when thickness is normal. 2, 7
If you develop vaginal bleeding, immediate evaluation is required regardless of endometrial thickness. 1, 2 The presence of symptoms changes the clinical context entirely and warrants endometrial sampling. 1
Follow-Up Recommendations
Repeat transvaginal ultrasound in 3-6 months is reasonable to ensure endometrial thickness remains stable in asymptomatic postmenopausal women. 2
If endometrial thickness increases to ≥5 mm on follow-up imaging, endometrial tissue sampling becomes necessary. 2
For asymptomatic postmenopausal women, biopsy should be considered only if endometrial thickness exceeds 11 mm. 5 At 3.1 mm, you are far below this threshold with an extremely low cancer risk of approximately 0.002%. 5