How to measure lining thickness? A Comprehensive Medical Overview

September 27, 2025 •

2 min read

According to research published by the NIH, transvaginal ultrasound is the cornerstone for evaluating endometrial health. This essential guide explains how to measure lining thickness using various medical imaging techniques, what factors can influence the results, and why this information is crucial for your reproductive and overall health.

Quick Summary

The thickness of the uterine lining, or endometrium, is primarily measured through a transvaginal ultrasound, a quick, non-invasive imaging test. Depending on the clinical need, a doctor may also use saline infusion sonohysterography for a more detailed view or perform an endometrial biopsy for a tissue sample.

Key Points

Primary Method: Transvaginal ultrasound (TVUS) is the most common and standard procedure for measuring the uterine lining's thickness.
Detailed Visualization: Saline infusion sonohysterography (SIS) uses saline to provide a clearer, fluid-enhanced view of the uterine cavity, especially for spotting polyps or fibroids.
Definitive Diagnosis: An endometrial biopsy involves taking a tissue sample for laboratory analysis, which is necessary for a definitive diagnosis of conditions like hyperplasia or cancer.
Timing Matters: Normal thickness varies significantly based on your menstrual cycle phase or menopausal status, so timing of the measurement is crucial.
Beyond Thickness: Doctors evaluate not only the measurement but also factors like your age, hormonal status, and symptoms to interpret the results accurately.
Abnormal Bleeding: For postmenopausal women, any vaginal bleeding requires a medical evaluation, regardless of endometrial thickness, to rule out serious conditions.

Understanding the Endometrium

The endometrium is the inner lining of the uterus, which changes in thickness throughout the menstrual cycle due to hormones. In reproductive years, it thickens for potential pregnancy and sheds during menstruation if conception doesn't occur. After menopause, it thins due to lower hormones. Measuring this lining is key for evaluating abnormal bleeding and fertility issues.

The Primary Method: Transvaginal Ultrasound (TVUS)

The most common way to measure endometrial thickness is with a transvaginal ultrasound. This in-office procedure uses a transducer inserted into the vagina, creating real-time images of the uterus and its lining on a monitor. The thickest part of the lining, the endometrial echo complex (EEC), is measured. The procedure typically takes 15–30 minutes.

Advanced Imaging: Saline Infusion Sonohysterography (SIS)

If a TVUS is unclear, a saline infusion sonohysterography (SIS) might be used. This involves filling the uterine cavity with saline via a catheter, which helps visualize polyps, fibroids, or other lesions by creating contrast.

Diagnostic Biopsy: Endometrial Sampling

If imaging raises concerns, an endometrial biopsy may be recommended. A small tissue sample is taken, often using a Pipelle, and analyzed in a lab for conditions like hyperplasia or cancer. This is crucial for postmenopausal women with thickened endometrium or bleeding.

Alternative Method: Magnetic Resonance Imaging (MRI)

MRI is another imaging option for measuring endometrial thickness, though it's less common for initial screening. {Link: ACOG https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2018/05/the-role-of-transvaginal-ultrasonography-in-evaluating-the-endometrium-of-women-with-postmenopausal-bleeding} for more details.

When is Your Lining Thickness Measured?

Timing depends on menstrual status and reason for the exam.

Premenopausal women: Measured just after menstruation (early proliferative phase) when thinnest. Thickness ranges from 2–4mm during menstruation up to 16mm in the secretory phase.
Postmenopausal women: Generally 5mm or less if not on hormone therapy. Any thickening or bleeding needs prompt TVUS and possibly a biopsy.
Fertility treatment: Monitored during IVF, especially before embryo transfer, for optimal thickness and pattern for implantation.

Factors Influencing Endometrial Thickness

Several factors affect thickness:

Hormones: Estrogen increases thickness; progesterone regulates it. Imbalances can cause issues.
Age: Thickness naturally decreases with age, especially after menopause.
Medical Conditions: PCOS, fibroids, and chronic endometritis can impact thickness.
Medications: HRT and some cancer treatments like tamoxifen affect growth.
Prior Surgeries: D&C and other uterine surgeries can cause scar tissue or adhesions.

Conclusion: Navigating Endometrial Health

Measuring lining thickness is crucial for gynecological health. While TVUS is standard, SIS and biopsy offer more detail when needed. Understanding these methods and influencing factors helps you discuss your health with your doctor. For more information on clinical guidelines, refer to sources like the American College of Obstetricians and Gynecologists(https://www.acog.org/). Always consult a medical professional for diagnosis and treatment.

Frequently Asked Questions

The primary method is a transvaginal ultrasound (TVUS), a quick and non-invasive procedure that uses sound waves to create an image of the uterine lining, or endometrium.

A TVUS is generally painless. You may feel some pressure from the transducer, similar to a pelvic exam, but it should not be painful. A lubricating gel is used to ensure comfort during insertion.

SIS measures the endometrial lining more clearly by using a sterile saline solution to distend the uterine cavity. This allows the doctor to see any focal lesions, like polyps or fibroids, that might be missed with standard ultrasound.

An endometrial biopsy is performed when imaging shows concerning results, such as a thickened endometrium, especially in postmenopausal women, or to investigate unexplained abnormal bleeding.

Normal endometrial thickness varies greatly depending on age and cycle phase. For premenopausal women, it fluctuates from 2–4mm during menstruation up to 16mm in the secretory phase. For postmenopausal women, a thickness of ≤ 5mm is typically considered normal.

No, measuring endometrial thickness requires professional medical equipment like an ultrasound machine and trained personnel. The procedure must be performed by a healthcare professional.

Several factors can influence the measurement, including your age, hormone levels (especially with HRT or tamoxifen use), medical conditions like PCOS or fibroids, and previous uterine surgeries.

Yes, an MRI may be used in more complex cases when a transvaginal ultrasound provides unclear images. It offers a detailed view of uterine structures but is not the standard first-line diagnostic tool.