Uterine fibroids, also known as leiomyomas or myomas, are common non-cancerous growths that develop within the uterus. They are the most frequent type of benign tumor affecting the female reproductive system, often appearing during the reproductive years. Estimates suggest that 70% to 80% of women will develop fibroids by the age of 50, though many never experience symptoms.
Uterine Fibroids Are Not Contagious
Uterine fibroids are not contagious and cannot be spread from one person to another. These growths are internal biological phenomena and are not infectious, meaning they are not caused by any type of pathogen. Fibroids do not result from viruses, bacteria, fungi, or any other transmissible infectious agent. Therefore, there is no risk of contracting fibroids through sexual intercourse, close contact, or any other form of physical interaction. The growths are self-contained tumors within the uterine tissue, and a person with fibroids poses no transmission risk to a partner or anyone else.
Defining Uterine Fibroids
A fibroid is a dense, non-cancerous tumor that originates from the smooth muscle cells and fibrous connective tissue of the uterine wall. These growths start when a single abnormal stem cell in the myometrium, the muscular layer of the uterus, divides repeatedly to form a firm, rubbery mass. While often referred to as tumors, in more than 99% of cases they are benign and do not increase the risk of developing uterine cancer. Fibroids vary dramatically in size, ranging from growths as small as a seed to large masses that can alter the shape of the uterus.
The location of the fibroid determines its classification, which also affects the symptoms a person might experience. Intramural fibroids are the most common type, developing and remaining within the muscular wall of the uterus itself. Subserosal fibroids grow on the outer surface of the uterus and can sometimes attach via a stalk, extending into the pelvic cavity. Submucosal fibroids are the least common type but tend to cause the most significant symptoms, as they grow just beneath the uterine lining and protrude into the uterine cavity. Some fibroids can also be pedunculated, meaning they are attached by a thin stalk. The size and specific location of these growths influence whether they cause issues such as heavy menstrual bleeding, pelvic pain, or pressure on the bladder.
Key Factors in Fibroid Development
Since fibroids are not infectious, their formation and growth are tied to a combination of internal biological and genetic factors. The growth of these tumors is strongly stimulated by reproductive hormones, particularly estrogen and progesterone. Fibroid cells contain more receptors for these hormones than regular uterine muscle cells, which explains why fibroids typically grow during the reproductive years and often shrink after menopause when hormone levels decline. Other substances, such as insulin-like growth factor, also appear to play a part in promoting fibroid growth and tissue maintenance.
Genetic predisposition is another significant factor, with fibroids tending to run in families, suggesting a hereditary component. Having a mother or sister with fibroids increases a person’s risk of developing them by approximately three times. Researchers have identified specific gene changes, notably mutations in the MED12 gene, that are frequently found in fibroid tissue, differing from those in typical uterine muscle cells.
Age is a non-modifiable risk factor, as fibroids are most commonly diagnosed in individuals in their 30s and 40s. Ethnicity also plays a role, as Black women are significantly more likely to develop fibroids, often at a younger age, and they tend to have larger or more numerous growths compared to women of other racial groups. High blood pressure and early onset of menstruation are additional factors linked to a greater likelihood of fibroid development.