Which Type Of Fibroid Is The Most Dangerous and Fibroids: What to Know

Uterine fibroids (also called leiomyomas) are very common noncancerous growths of the muscle of the uterus. Most fibroids are harmless, but some can cause heavy bleeding, anemia, infertility, or pregnancy complications. This article explains which fibroids tend to be most concerning, how to recognize symptoms, and the evidence-based options to diagnose and treat them.

Types of Fibroids and Why Location Matters

Doctors usually describe fibroids by where they grow:

• Submucosal: Just beneath the uterine lining and bulging into the uterine cavity.
• Intramural: Within the muscular wall of the uterus (the most common type).
• Subserosal: On the outer surface of the uterus.
• Pedunculated: Attached by a stalk (can be inside or outside the uterus).
• Cervical: In or on the cervix (less common).

Symptoms and risks are driven more by size and location than by the name of the fibroid itself. A small fibroid in a sensitive location can cause more problems than a large one elsewhere.

So, Which Type Is the Most Dangerous?

“Dangerous” can mean different things—life-threatening, threatening to fertility, or severely impacting quality of life. Here’s how specialists think about risk:

• Most dangerous for heavy bleeding and anemia: Submucosal fibroids distort the uterine cavity and are strongly linked to heavy menstrual bleeding. Untreated, this can lead to iron-deficiency anemia, fatigue, and, rarely, the need for urgent transfusion.
• Most disruptive to fertility: Submucosal (and some intramural fibroids that distort the cavity) can impair implantation, increase miscarriage rates, and reduce chances of pregnancy. Removing submucosal fibroids can improve fertility in many cases.
• Risk of acute pain or emergency: Pedunculated subserosal fibroids can twist (torsion), cutting off their blood supply and causing sudden, severe pain that may require urgent surgery.
• Obstructive complications: Large cervical fibroids can block the cervical canal, leading to labor obstruction or difficulty with menstrual flow or procedures.
• Mass effect: Very large intramural or subserosal fibroids can compress the bladder or bowel, causing urinary frequency, constipation, or back pain.

Importantly, fibroids are benign. A malignant tumor of the uterus called leiomyosarcoma is rare and is generally not believed to arise from preexisting fibroids. Because imaging cannot reliably distinguish the two in every case, the U.S. Food and Drug Administration (FDA) has issued safety communications for certain surgical techniques (such as power morcellation) due to a small risk of encountering an unexpected uterine cancer during surgery for presumed fibroids. The overall risk is very low, but decisions about surgery should be individualized and discussed with your surgeon.

Who Is at Higher Risk of Fibroids?

Fibroids are most common in people aged 30–50. They can occur earlier and continue after menopause, though they often shrink when estrogen levels decline. Studies show that Black women are more likely to develop fibroids, to have multiple or larger fibroids, and to experience more severe symptoms. Other risk factors include family history, earlier age at first period, obesity, and not having given birth.

Symptoms to Watch For

• Heavy or prolonged menstrual bleeding (changing pads/tampons hourly for several hours, passing large clots)
• Pelvic pressure or pain
• Frequent urination or difficulty emptying the bladder
• Constipation or bloating
• Pain with intercourse
• Infertility, recurrent miscarriage, or complications during pregnancy

Seek urgent care if you have heavy bleeding causing dizziness or fainting, severe pain with fever, a rapidly enlarging abdominal mass, or any severe symptoms during pregnancy.

How Fibroids Are Diagnosed

• Pelvic exam: May detect an enlarged or irregularly shaped uterus.
• Ultrasound (transvaginal and/or transabdominal): First-line imaging to identify size, number, and location.
• Saline infusion sonohysterography or hysteroscopy: Helpful to evaluate the uterine cavity, especially for suspected submucosal fibroids.
• MRI: Details size and mapping for complex cases or surgical planning.

Treatment Options: From Watchful Waiting to Surgery

The best approach depends on your symptoms, goals (such as preserving fertility or the uterus), overall health, and the fibroid’s size and location.

Non-surgical options

• Watchful waiting: If symptoms are mild, periodic check-ins and iron monitoring may be enough.
• Medications for bleeding and pain:
  • NSAIDs (e.g., ibuprofen) can reduce menstrual pain and some bleeding.
  • Tranexamic acid reduces heavy menstrual bleeding during periods.
  • Hormonal options: Combined oral contraceptives or progestin-only methods can help control bleeding; a levonorgestrel-releasing IUD can markedly reduce bleeding for many patients with appropriate uterine anatomy.
• Hormonal suppression and shrinkage:
  • GnRH agonists (e.g., leuprolide) temporarily shrink fibroids and are often used short-term to correct anemia or before surgery.
  • Oral GnRH antagonists with add-back therapy are FDA-approved for heavy menstrual bleeding due to fibroids, including elagolix/estradiol/norethindrone (Oriahnn) and relugolix/estradiol/norethindrone (Myfembree). These can reduce bleeding and sometimes shrink fibroids; add-back hormones help mitigate bone loss and hot flashes. Duration limits and monitoring apply.

Uterus-sparing procedures

• Hysteroscopic myomectomy: Removes submucosal fibroids through the cervix; often improves heavy bleeding and fertility.
• Laparoscopic or open myomectomy: Removes fibroids while preserving the uterus; appropriate for intramural or subserosal fibroids, especially in those desiring future pregnancy.
• Uterine fibroid embolization (UFE): An interventional radiology procedure that blocks blood flow to fibroids, shrinking them and reducing bleeding/pressure. Not ideal for everyone planning future pregnancy; discuss individualized risks.
• Radiofrequency ablation (laparoscopic or transcervical) and MRI-guided focused ultrasound: Minimally invasive options that destroy fibroid tissue; suitability depends on size, number, and location.

Definitive treatment

• Hysterectomy: Removes the uterus and completely resolves fibroid-related bleeding and bulk symptoms. It is definitive and eliminates future pregnancies; ovarian-sparing approaches can preserve hormones in appropriate patients.

Fibroids and Pregnancy: What to Know

Many people with fibroids have healthy pregnancies. However, fibroids—especially submucosal and some intramural types that distort the cavity—are associated with a higher risk of miscarriage, preterm birth, fetal malpresentation (breech), cesarean delivery, and postpartum hemorrhage. Fibroids can also grow during pregnancy due to hormonal changes, sometimes causing pain (degeneration). Close prenatal monitoring is important, and severe pain, bleeding, fever, or contractions before term warrant urgent evaluation. If fertility is a goal, discuss timing and type of treatment with your obstetrician-gynecologist or reproductive specialist before trying to conceive.

When to Talk to a Clinician

Consult a healthcare professional if you have heavy or prolonged periods, anemia, pelvic pressure or pain, trouble getting pregnant, or rapidly changing symptoms—especially after menopause. Shared decision-making with a gynecologist experienced in fibroid care can help you weigh benefits, risks, recovery, and future fertility.

Key Takeaways

• Submucosal fibroids are most likely to cause heavy bleeding and fertility problems.
• Pedunculated fibroids can twist and cause acute pain that may require urgent care.
• Most fibroids are benign; unexpected uterine cancers are rare, but surgical choices should consider FDA safety guidance.
• Treatments range from medication to minimally invasive procedures and surgery—tailored to your symptoms and goals.

This article is for educational purposes and does not replace medical advice. Always consult your clinician about your specific situation.

Sources (Trusted Health Authorities)

• National Institutes of Health (NIH), Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). Uterine fibroids overview: nichd.nih.gov
• MedlinePlus, U.S. National Library of Medicine: Uterine fibroids: medlineplus.gov
• American College of Obstetricians and Gynecologists (ACOG). Uterine Fibroids—FAQ and Practice Guidance: acog.org
• U.S. Food and Drug Administration (FDA). Safety communications on surgical power morcellation and risk of unsuspected uterine sarcoma: fda.gov
• FDA drug information on therapies for heavy menstrual bleeding due to fibroids: Oriahnn (elagolix/estradiol/norethindrone) and Myfembree (relugolix/estradiol/norethindrone): fda.gov/Oriahnn and fda.gov/Myfembree
• Centers for Disease Control and Prevention (CDC). Iron-deficiency anemia: cdc.gov