What is the normal thickness of the endometrium (uterine lining) in a postmenopausal woman?

Normal Endometrial Thickness in Postmenopausal Women

In postmenopausal women, the endometrium should measure 4 mm or less by transvaginal ultrasound, which provides a nearly 100% negative predictive value for endometrial cancer. 1

Threshold Values and Clinical Significance

• The American College of Radiology establishes 4 mm as the upper limit of normal endometrial thickness in postmenopausal women, measured using the double-layer technique on transvaginal ultrasound 1

• An endometrial thickness ≤4 mm effectively excludes endometrial malignancy with a negative predictive value approaching 100% 1, 2

• When endometrial thickness measures ≥5 mm, endometrial tissue sampling is generally recommended to rule out hyperplasia or malignancy 1

• The European Society for Medical Oncology uses a slightly more conservative threshold of ≤3 mm, though the 4 mm cutoff is more widely accepted in clinical practice 1

Measurement Technique

• Transvaginal ultrasound should be combined with transabdominal ultrasound whenever possible for complete pelvic assessment 1

• The measurement includes both endometrial layers (double-layer technique) at the thickest part in the longitudinal plane 3, 2

• Transvaginal ultrasound is the first-line screening test for evaluating endometrial thickness in postmenopausal women 1

Clinical Context and Body Weight Correlation

• In asymptomatic postmenopausal women, endometrial thickness correlates with body weight and body mass index (BMI), with heavier women more likely to have thicker endometrium even in the absence of pathology 4

• The mean endometrial thickness in asymptomatic postmenopausal women without bleeding ranges from 1.4-2.3 mm 5, 4

• Women with endometrial thickness <5 mm who are asymptomatic require no further evaluation 1

Important Caveats

• Ultrasound is sensitive for measuring thickness but cannot reliably determine the etiology of endometrial thickening 1

• Abnormal echogenicity and texture of the endometrium may indicate pathology even when thickness appears normal, so the ultrasound report should comment on endometrial appearance, not just thickness 1, 6

• If repeat imaging continues to show endometrium <4 mm, the negative predictive value for cancer remains nearly 100% 1

• In the presence of postmenopausal bleeding, even an endometrium >5 mm warrants investigation regardless of other factors 7