Thick womb lining found by chance after menopause

The main guidance

ACOG Committee Opinion 734 (US): on ultrasound of the womb lining after menopause, mainly with bleeding, with one statement on a thicker lining found without bleeding. May 2018, reaffirmed 2023. (ACOG CO 734)
SOGC Guideline No. 451 (Canada): a guideline just for a thicker lining found on ultrasound after menopause in someone without bleeding, published July 2024. Its stated aim is fewer needless tests while selectively checking people at risk of womb cancer. (SOGC 451)
NICE NG12 (UK): when bleeding after menopause should lead to a suspected cancer referral, by age. (NICE NG12)

Who it applies to

SOGC No. 451 covers people after menopause of any age who have no bleeding. (SOGC 451) The NHS says menopause is usually diagnosed in women over 45 who have not had a period for more than a year. (NHS) If you have had any bleeding after menopause, this page is not the right guide: see bleeding changes the plan.

The thickness numbers

Womb lining thickness after menopause and what guidance says (simplified)
Situation	Number used	What it means
Average, no bleeding	About 2.9 mm	The pooled average in studies of people not using hormone therapy (Breijer 2012)
With bleeding (ACOG)	4 mm or less	Over 99% negative predictive value for womb cancer, so ultrasound is usually enough as a first check (ACOG CO 734)
With bleeding (SRU 2001)	Over 5 mm	Read as abnormal; some panel members preferred 4 mm (Giri 2021)
No bleeding (ACOG)	Over 4 mm	Need not routinely trigger more tests; individual assessment by risk factors (ACOG CO 734)
No bleeding (SOGC)	Under 11 mm	Rarely a serious problem, but should be looked at by a health care provider (SOGC 451)
No bleeding (SOGC, per review)	Over 11 mm	Further evaluation (Giri 2021)

The bleeding numbers are lower because bleeding is itself a warning sign: ACOG says vaginal bleeding is the first sign in more than 90% of people after menopause who have womb cancer. (ACOG CO 734)

What else changes the plan

How the lining looks: the open review by Giri and colleagues says SOGC lists more blood flow, an uneven (inhomogeneous) lining or fluid with particles as reasons for more evaluation, whatever the thickness. (Giri 2021)
Your risk factors: ACOG lists age, obesity, estrogen taken without a progestin, polycystic ovary syndrome, type 2 diabetes, atypical glandular cells on cervical screening and a family history of gynecologic cancer. (ACOG CO 734)
Any bleeding, spotting or new discharge after menopause: see the next section. (MedlinePlus)

ACOG and SOGC do not set one fixed time for a repeat ultrasound in their summaries; both call for an assessment of the person by their provider. (ACOG CO 734)(SOGC 451)

Bleeding changes the plan

NHS: see a GP for bleeding from the vagina after menopause, even if it is a small amount or happened only once. A GP should refer you to hospital or a postmenopausal bleeding clinic, and you should not have to wait more than 2 weeks to see a specialist. (NHS)
NICE: refer people aged 55 and over with unexplained bleeding after menopause on a suspected cancer pathway, and consider it under 55. (NICE NG12)
ACOG: bleeding after menopause needs prompt and efficient evaluation. (ACOG CO 734)

Ultrasound is not a screening test here

ACOG says transvaginal ultrasound is not an appropriate screening test for womb cancer in people after menopause without bleeding. (ACOG CO 734) A 2012 review of 32 studies (11,100 women) found womb cancer in about 0.62% and atypical hyperplasia in about 0.59%, and concluded the results do not justify lining thickness as a screening test. (Breijer 2012) MedlinePlus says there is no effective screening test for endometrial cancer. (MedlinePlus) For more, see endometrial cancer screening.

MedlinePlus, when to contact a medical professional. Contact your provider for an appointment if you have any of the following: (MedlinePlus)

Any bleeding or spotting that occurs after the onset of menopause
Bleeding or spotting after intercourse or douching
Bleeding lasting longer than 7 days
Irregular menstrual cycles that occur twice per month
New discharge after menopause has begun
Pelvic pain or cramping that does not go away

Routine age-based screening

A finding on a scan does not replace the routine screenings for your age; see screenings after menopause. If the same scan showed something on an ovary, see ovarian cyst found by chance.

Where they differ:

Which number, without bleeding. ACOG gives no fixed number and says over 4 mm need not routinely lead to more tests. (ACOG CO 734) SOGC uses 11 mm as the point below which it is rarely a serious problem. (SOGC 451) A 2023 review of 18 studies (10,334 women) found the risk was raised by a similar amount at every cut-off from 3 mm to over 14 mm; lower cut-offs found more cases but gave more false alarms. (Vitale 2023)
Which number, with bleeding. ACOG uses 4 mm or less as reassuring; the SRU 2001 statement read over 5 mm as abnormal. (ACOG CO 734)(Giri 2021)
Age for referral. NICE uses age 55 to decide between a referral and considering one when there is bleeding; ACOG and SOGC do not use an age cut-off in their summaries. (NICE NG12)(ACOG CO 734)(SOGC 451)

Your doctor decides what your result means for you.

Questions people ask

Does a thicker lining found by chance mean cancer?

Usually not. ACOG says a lining over 4 mm found by chance without bleeding need not routinely lead to more tests, and SOGC says under 11 mm is rarely a serious problem. (ACOG CO 734) (SOGC 451)

Why is 4 mm used for bleeding but not here?

With bleeding, ACOG says 4 mm or less rules out cancer with over 99% certainty. Without bleeding, ACOG says over 4 mm need not routinely trigger more tests; the plan depends on you. (ACOG CO 734)

Should I have regular ultrasounds to check my lining?

ACOG says transvaginal ultrasound is not an appropriate screening test for womb cancer in people without bleeding after menopause. (ACOG CO 734) (Breijer 2012)

What if I start bleeding later?

Get it checked. The NHS says see a GP for any bleeding after menopause, even a small amount or once. MedlinePlus lists any bleeding or spotting after menopause as a reason to contact your provider. (NHS) (MedlinePlus)

What else on the scan matters besides thickness?

The open review by Giri and colleagues says SOGC lists more blood flow, an uneven lining or fluid with particles as reasons for more evaluation, as well as a lining over 11 mm. (Giri 2021)