Endometrial Polyps and Fertility: Small Growths That Can Quietly Block Implantation

Endometrial polyps are one of the more common findings during a fertility scan and one of the easiest conditions to underestimate. They are small, usually harmless growths that develop in the lining of the uterus (endometrium), often measuring only a few millimetres. Most polyps cause no symptoms, and many women only discover they have one during an ultrasound performed for another reason.

Although they may appear insignificant, endometrial polyps can affect fertility because the uterine lining is where an embryo must implant. A polyp occupying this space can quietly reduce the chances of successful implantation, even when egg quality, embryo quality, and hormone levels are all normal. They are a common and highly treatable cause of unexplained infertility and repeated IVF implantation failure.

This guide is intended for women who have recently been diagnosed with an endometrial polyp or who have experienced unsuccessful embryo transfers without a clear explanation.

What Is an Endometrial Polyp?

An endometrial polyp is a localized overgrowth of the uterine lining. It develops when endometrial glands, connective tissue, and small blood vessels grow together, forming a projection that extends into the uterine cavity. Some polyps grow on a thin stalk, while others remain attached directly to the uterine wall.

Endometrial polyps are relatively common. Studies estimate they occur in approximately 8% to 35% of women overall and in around 15% to 24% of women undergoing fertility investigations. One study involving 1,000 women found polyps in nearly one-third of hysteroscopies performed before IVF treatment.

Most polyps are benign, particularly in women of reproductive age. Their growth is largely influenced by estrogen, which explains why they may enlarge or recur over time. The risk of cancer is very low in younger women and becomes more significant mainly after menopause, particularly when abnormal bleeding is present.

Why Do Endometrial Polyps Often Go Undetected?

Most endometrial polyps produce no noticeable symptoms, making them easy to miss.

When symptoms do occur, they commonly include:

• Spotting between menstrual periods.
• Heavy or prolonged menstrual bleeding.
• Bleeding after sexual intercourse.

However, many women experience none of these symptoms. During fertility treatment, polyps are frequently discovered during routine ultrasound examinations or after repeated failed embryo transfers when doctors investigate possible causes of implantation failure.

A polyp may remain inside the uterus for years without causing discomfort while quietly affecting fertility.

How Endometrial Polyps Affect Embryo Implantation

Endometrial polyps can interfere with implantation in several different ways, and the effects are not purely mechanical.

Physically, a polyp occupies valuable space within the uterine cavity, potentially preventing an embryo from attaching successfully. Polyps located near the openings of the fallopian tubes (utero-tubal junction) may also interfere with sperm transport or fertilization.

Research has shown that pregnancy rates improve significantly after removing polyps located in this area.

Beyond the physical obstruction, polyps also alter the biological environment of the uterus by:

• Increasing inflammatory activity within the endometrium.
• Producing glycodelin, a protein that may interfere with sperm function and embryo implantation.
• Reducing the receptivity of the uterine lining.

These biological changes help explain why even relatively small polyps can reduce implantation rates and contribute to recurrent implantation failure.

How Are Endometrial Polyps Diagnosed?

Most endometrial polyps are first detected during a transvaginal ultrasound, ideally performed during the first half of the menstrual cycle when the uterine lining is thinner.

Because small polyps can sometimes resemble folds in the endometrium or small fibroids, additional investigations may be recommended.

Diagnostic options include:

• Transvaginal Ultrasound – Often the first imaging test.
• Saline Infusion Sonography (Saline Scan) – Sterile fluid is introduced into the uterus to improve visualization of the uterine cavity.
• Hysteroscopy – A thin camera is inserted into the uterus, allowing direct visualization and immediate removal of the polyp if necessary.

Hysteroscopy remains the most accurate method for both diagnosis and treatment.

How Does Removing a Polyp Improve Fertility?

The evidence supporting hysteroscopic polypectomy is encouraging.

During this minimally invasive outpatient procedure, the polyp is removed under direct visualization, making it more precise than older blind curettage techniques.

Research has shown:

• Women undergoing intrauterine insemination (IUI) experience approximately a four-fold increase in pregnancy rates after polyp removal.
• Cumulative pregnancy rates improve from approximately 18% without treatment to around 38% after hysteroscopic removal.
• Women undergoing IVF after previous failed cycles have reported clinical pregnancy rates approaching 65% following polypectomy.
• Several studies also demonstrate significantly improved natural conception rates after removal, with pregnancy rates reaching nearly 78% in some patient groups.

Although IVF studies are mainly observational, the overall evidence consistently supports removing polyps before fertility treatment.

When Should an Endometrial Polyp Be Removed?

Not every endometrial polyp requires immediate treatment.

For women who are not trying to conceive and have no symptoms, small polyps can often be monitored without intervention.

However, recommendations change when fertility treatment is planned.

Most fertility specialists advise removing polyps before:

• IVF treatment.
• Intrauterine insemination (IUI).
• Frozen embryo transfer (FET).

Current research suggests that even small polyps may negatively affect implantation, and there is no reliable size below which a polyp can safely be ignored.

Timing is also important. A hysteroscopic polypectomy should not be performed immediately before embryo transfer because the uterine lining requires adequate time to heal. The procedure is typically completed during a treatment cycle before the planned embryo transfer.

Additional Things to Know About Endometrial Polyps

There are two additional points worth remembering:

• Endometrial polyps can recur, so repeat evaluation may be recommended if fertility problems continue.
• The hysteroscopy itself may slightly improve endometrial receptivity, potentially providing an additional benefit beyond simply removing the polyp.

Conclusion

Although endometrial polyps are usually benign, they can significantly affect embryo implantation and fertility outcomes. Fortunately, they are among the most treatable causes of unexplained infertility and repeated IVF failure.

If an ultrasound has identified a uterine polyp or you've experienced repeated unsuccessful embryo transfers without a clear explanation, evaluating and treating the uterine lining before your next fertility treatment may improve your chances of success.

Book a consultation with MMC IVF to discuss your fertility assessment and receive a personalized treatment plan designed to optimize your chances of a successful pregnancy.

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