Uterine fibroids: what makes them grow, what can make them shrink? The truth based on scientific evidence

Uterine fibroids (also called myomas or leiomyomas) are benign tumors that develop from the muscular layer of the uterus. They are very common: up to 70% of women may develop them during their lifetime. However, their evolution varies greatly: some remain stable for years, others gradually increase in size, while some may even decrease spontaneously.

A common question from many patients is: “What makes a fibroid grow? And what can I do to reduce it?”

Hormones: the main factor

Fibroids are strongly influenced by female hormones, especially estrogen and progesterone. They rarely appear before puberty and tend to grow during the reproductive years, then often regress after menopause when hormone levels decrease.

Histological studies have shown that fibroid cells contain estrogen and progesterone receptors, which explains their hormone sensitivity (Bulun SE. Endocrine Reviews, 2013).

Pregnancy: growth is possible, but not inevitable

During pregnancy, estrogen and progesterone levels increase significantly. As a result, some fibroids may enlarge, particularly during the first trimester.

However, pregnancy does not automatically mean that a fibroid will continue to grow permanently. Ultrasound studies show considerable variability: some fibroids increase in size, some remain stable, and some even decrease during pregnancy (Laughlin SK et al. Obstetrics & Gynecology, 2011).

After delivery, spontaneous reduction in fibroid volume is common.

Ovarian stimulation during assisted reproductive medicine (ART)

Fertility treatments (ovarian stimulation, intrauterine insemination, in vitro fertilization) expose the body temporarily to higher hormone levels.

This raises a legitimate question: Can fertility treatments make fibroids grow?

Current evidence does not clearly demonstrate that ovarian stimulation causes significant and permanent fibroid growth. Some women may experience temporary changes related to hormonal fluctuations.

The impact of fibroids on fertility depends mainly on their location:

• fibroids that distort the uterine cavity may affect implantation and fertility;

• fibroids located within the uterine muscle or on the outer surface of the uterus often have a different clinical impact.

Therefore, management should always be individualized.

Contraception: combined pills, hormonal IUD and other methods

Combined oral contraceptive pills

Older studies sometimes suggested an increased risk of fibroids with prolonged hormonal exposure. More recent data are more nuanced, and some studies even suggest a possible protective effect.

Progestin methods and levonorgestrel intrauterine device (hormonal IUD)

The hormonal IUD can effectively reduce heavy bleeding associated with fibroids, mainly through its local effect on the uterine lining. However, it does not systematically make the fibroid itself disappear.

Non-hormonal contraception

There is currently no strong evidence that non-hormonal contraception causes fibroids to shrink.

Diet and environmental factors: what do we really know?

Some factors appear to be associated with the risk of developing fibroids:

• Overweight and obesity: Several studies show an association between a higher body mass index and an increased risk of fibroids. Fat tissue can increase peripheral conversion of androgens into estrogens (Wise LA et al. American Journal of Epidemiology, 2005).

• Diet rich in fruits and vegetables: Some observational studies suggest a slightly lower risk, possibly due to fiber, vitamins and antioxidant compounds.

• High intake of red meat and calorie-dense diets: Some associations have been observed, but they do not prove a direct cause-and-effect relationship.

Regarding endocrine disruptors (plastics, certain pesticides, etc.), biological mechanisms are plausible, but human evidence remains insufficient to recommend specific measures beyond general reduction of unnecessary exposure.

Plants, supplements and “natural treatments”

Many products are promoted online as being able to “dissolve” fibroids. To date, no plant or dietary supplement has been robustly proven to permanently reduce fibroid size.

Some natural compounds are being studied, such as vitamin D and epigallocatechin gallate (a component of green tea), but clinical evidence remains insufficient to consider them validated treatments.

Vitamin D deserves particular attention: several observational studies have found an association between vitamin D deficiency and the presence of fibroids. However, it has not yet been proven that vitamin D supplementation can reduce an existing fibroid.

Medications: can fibroids disappear with treatment?

Some medications can temporarily reduce fibroid volume:

• GnRH agonists can cause significant reduction in fibroid size, but their use is generally limited because of side effects related to low estrogen levels.

• Specific hormonal modulators may be used in selected situations depending on local recommendations.

These treatments are mainly used for specific indications, for example before surgery.

Does every fibroid need treatment?

The presence of a fibroid does not automatically mean that treatment is required.

The decision depends on several factors:

• symptoms (heavy bleeding, pain, pelvic pressure),

• size and location,

• changes over time,

• desire for pregnancy,

• possible impact on fertility.

Many fibroids only require regular ultrasound monitoring.

In summary

A fibroid is a benign tumor that is sensitive to hormones. Its growth depends mainly on individual hormonal factors. Pregnancy and fertility treatments may influence its evolution temporarily, but there is currently no proven natural method to make a fibroid disappear.

The best approach remains a personalized evaluation and appropriate follow-up: the same fibroid may have no consequences for one woman and require treatment in another.

Kindly yours,

Dr Sandra Yene Amougui