Gynecology · Endometrial Polyps

Understanding Uterine Polyps: Biology and Symptoms

At a Glance

Uterine polyps are usually benign growths from the uterine lining, but they can cause spotting, heavy or irregular bleeding, postmenopausal bleeding, or fertility difficulties. Any postmenopausal bleeding and very heavy bleeding should be medically evaluated.

Uterine polyps, also known as endometrial polyps, are small, finger-like growths that develop from the inner lining of the uterus (the endometrium) ^[1]. While they are overwhelmingly benign (non-cancerous), they can cause disruptive symptoms, trigger anxiety, or interfere with fertility ^[2]. Understanding how these growths form and how they differ from other common uterine issues is an important first step in managing your gynecological health.

How Polyps Form

A polyp begins as a focal overgrowth of the uterine lining ^[1]. Unlike the rest of the lining, which thickens and sheds every month during a period, these growths stay attached to the uterine wall by a base or a thin stalk ^[1].

Biologically, polyps are made of a mix of endometrial glands, connective tissue (stroma), and thick-walled blood vessels ^[1]. Research suggests that hormones—specifically estrogen and progesterone—play a key role in their development ^[3]. In many cases, polyps show a higher number of estrogen receptors and a lower number of progesterone receptors compared to the healthy surrounding tissue ^[3]. This hormonal imbalance may cause that specific spot to grow excessively rather than shedding normally ^[4].

Symptom Patterns by Life Stage

Not every polyp causes symptoms; many are found incidentally during a routine exam or an ultrasound for an unrelated reason ^[5]. However, when symptoms do occur, they often follow specific patterns depending on whether you have reached menopause.

Premenopausal Women: The most characteristic symptom is intermenstrual bleeding, which is spotting or bleeding that occurs between your normal periods ^[2]. You may also experience heavy menstrual bleeding (menorrhagia) or irregular cycles where the timing of your period becomes unpredictable ^[6]^[7]. If you experience very heavy bleeding that causes dizziness, shortness of breath, or requires changing a pad every hour, seek prompt medical evaluation for anemia or acute blood loss.
Postmenopausal Women: In people who have finished menopause, any vaginal bleeding is considered abnormal and should be evaluated promptly ^[8]. Polyps are one possible cause of postmenopausal bleeding ^[9]. However, a polyp’s presence does not rule out other causes, such as vaginal atrophy or cancer, so a thorough evaluation is always necessary.
Fertility Concerns: Polyps can act like a physical barrier or cause local inflammation that makes it harder for an embryo to attach to the uterine wall, potentially leading to subfertility (difficulty getting pregnant) ^[2]^[8].

Polyps vs. Fibroids

It is common to confuse polyps with uterine fibroids (leiomyomas), but they are fundamentally different types of growths. Their symptoms can overlap significantly, so imaging is required to tell them apart.

Feature	Uterine Polyp	Uterine Fibroid
Origin	Grows from the inner lining (endometrium) ^[1].	Grows from the muscle of the uterine wall (myometrium) ^[10].
Composition	Glands, stroma, and blood vessels ^[1].	Dense, fibrous muscle tissue ^[11].
Typical Size	Usually small (millimeters to a few centimeters) ^[12].	Can range from tiny to the size of a grapefruit or larger ^[13].
Typical Symptoms	Focal spotting and irregular or intermenstrual bleeding ^[2].	Heavy periods, pelvic pressure, and “bulk” symptoms ^[13], though submucosal fibroids can also cause spotting.

Who is at Risk?

While anyone with a uterus can develop a polyp, certain factors increase the likelihood:

Age and Menopause: The risk generally increases as you get older, peaking in your 40s and 50s ^[14].
Weight and Metabolism: Having a higher BMI (Body Mass Index), diabetes, or high blood pressure (hypertension) is linked to a higher incidence of polyps ^[15]^[5].
Tamoxifen Use: Patients taking tamoxifen for breast cancer treatment have a significantly higher risk of developing endometrial polyps because of how the drug affects the uterine lining ^[16].

Prevalence: How Common Are They?

Because many polyps have no symptoms, it is hard to say exactly how many people have them in the general population. Estimates vary widely, from roughly 8% to 30% depending on the age group and the imaging tools used ^[17]. However, among those who seek medical help for abnormal uterine bleeding (AUB), polyps are found much more frequently—detected in approximately 34% to 38% of cases ^[18]^[19].

While the vast majority of polyps are benign, pooled studies suggest a small percentage (an average of about 3.4% across populations) may contain precancerous or cancerous cells ^[20]^[21]. This is a population average, not an individual guarantee. This risk is generally higher for postmenopausal patients or those who are experiencing active bleeding, which is why testing is highly recommended in those situations ^[20]^[12].

Common questions in this guide

What exactly is a uterine polyp, and how does it develop?

A uterine polyp, also called an endometrial polyp, is usually a benign overgrowth from the inner lining of the uterus. It contains glands, supporting tissue, and blood vessels and may remain attached by a broad base or a thin stalk.

What bleeding changes can uterine polyps cause?

They can cause spotting between periods, heavier periods, or cycles that become irregular. Some polyps cause no symptoms and are found during an examination or ultrasound done for another reason.

Does bleeding after menopause mean I have a uterine polyp?

No. A polyp is one possible cause, but vaginal bleeding after menopause can also come from tissue thinning or cancer, so even one episode should be evaluated promptly.

How are uterine polyps different from fibroids?

Polyps grow from the inner uterine lining, while fibroids grow from the muscular wall of the uterus. Their symptoms can overlap, so imaging may be needed to tell them apart.

Can a uterine polyp make it harder to get pregnant?

Yes, a polyp can act as a physical barrier or create local inflammation that makes it harder for an embryo to attach to the uterine wall. This may contribute to difficulty getting pregnant, although it does not affect everyone with a polyp.

Are uterine polyps cancerous?

Most uterine polyps are benign, but a small percentage contain precancerous or cancerous cells. The risk is generally higher after menopause or when bleeding is present, so a clinician may recommend testing based on your age, symptoms, and findings.

Who is more likely to develop uterine polyps?

Risk tends to rise with age, especially in the 40s and 50s, and is also linked with a higher body mass index, diabetes, and high blood pressure. Tamoxifen use for breast cancer is another recognized risk factor.

Guide Contents

Understanding Uterine Polyps: Biology and Symptoms

How Polyps Form

Symptom Patterns by Life Stage

Polyps vs. Fibroids

Who is at Risk?

Prevalence: How Common Are They?

Common questions in this guide

Appointments are short. Make every minute count.

Related questions

Get notified when new evidence is published on uterine polyp.

Guide Contents

How Polyps Form

Symptom Patterns by Life Stage

Polyps vs. Fibroids

Who is at Risk?

Prevalence: How Common Are They?

Common questions in this guide

Appointments are short. Make every minute count.

Related questions

Get notified when new evidence is published on uterine polyp.

References