There is no proven way to completely stop fibroids from growing during pregnancy, but the picture is more reassuring than most people expect. Research from the American Journal of Obstetrics and Gynecology found that fibroids typically grow by about 27% between the first and second trimesters, then shrink by about 24% between the second and third trimesters, resulting in an overall decrease of roughly 15% by the end of pregnancy. Smaller fibroids are actually more likely to grow (57% of them do), while the majority of large fibroids stay stable. So the pattern for most women is a temporary mid-pregnancy increase followed by a natural decline.
That said, there are real steps you can take to limit the factors that fuel fibroid growth and manage any symptoms that arise.
Why Fibroids Grow During Pregnancy
Fibroids are highly sensitive to two hormones that surge during pregnancy: estrogen and progesterone. Progesterone drives fibroid cell proliferation directly, while estrogen amplifies that effect by increasing the number of progesterone receptors on fibroid tissue. Together, they trigger mature fibroid cells to release growth signals to surrounding immature cells, essentially recruiting new tissue into the fibroid. This hormonal environment is unavoidable during pregnancy, which is why no intervention can guarantee fibroids won’t enlarge at all.
Stress may add fuel to this process. Cortisol, the body’s primary stress hormone, can cause fluctuations in estrogen and progesterone levels through its effect on the hormonal feedback loop between the brain and ovaries. While the direct link between stress and fibroid growth during pregnancy hasn’t been isolated in clinical trials, the biological pathway is plausible enough that managing stress is a reasonable precaution.
Vitamin D and Fibroid Growth
Vitamin D is one of the most studied nutrients in fibroid research, and the findings are striking. Vitamin D deficiency is a significant risk factor for fibroids, and fibroid tissue itself expresses lower levels of vitamin D receptors compared to normal uterine muscle. The active form of vitamin D functions as a potent anti-estrogen and anti-progesterone agent, which is precisely why it appears to slow fibroid growth.
In a clinical trial comparing vitamin D supplementation to placebo in women with deficient levels, fibroids in the vitamin D group shrank significantly (averaging about 53 mm) compared to the placebo group (about 61 mm). Animal studies have shown that vitamin D treatment reduces the number of estrogen and progesterone receptors on fibroid cells, cutting off the hormonal signals that drive growth.
If you haven’t had your vitamin D levels checked, it’s worth doing early in pregnancy. Prenatal vitamins contain some vitamin D, but women who are deficient often need higher amounts. Your provider can test your levels with a simple blood draw and adjust your intake accordingly.
Diet and Blood Sugar Control
What you eat can influence fibroid behavior through an indirect but well-documented pathway. Diets high in refined carbohydrates and sugar cause repeated spikes in blood sugar and insulin. Chronically elevated insulin increases the circulating levels of a growth factor called IGF-I, which fibroid cells are especially responsive to. Fibroid tissue produces more IGF-I protein and has greater IGF-I gene activity than normal uterine muscle. High insulin also reduces a protein that keeps estrogen bound and inactive in the blood, effectively increasing the amount of estrogen available to fuel fibroid growth.
A large study of over 22,000 women in the Black Women’s Health Study found that a high glycemic index diet was associated with increased fibroid risk, with the strongest associations in women under 35. While this research looked at fibroid development rather than growth during pregnancy specifically, the underlying biology applies: keeping blood sugar stable reduces two key drivers of fibroid proliferation.
In practical terms, this means prioritizing whole grains over white bread and pasta, pairing carbohydrates with protein or healthy fats to blunt blood sugar spikes, and limiting sugary drinks and processed snacks. These are standard recommendations for a healthy pregnancy anyway, but they carry extra relevance if you have fibroids.
Stress Reduction During Pregnancy
The connection between major life stress and fibroid presence has been documented in cohort studies. Cortisol released during chronic stress disrupts the normal regulation of estrogen and progesterone, and those are the two hormones most responsible for fibroid growth. While you can’t eliminate stress entirely during pregnancy, consistent stress management practices like walking, prenatal yoga, adequate sleep, and social support may help keep cortisol from compounding the hormonal environment that fibroids thrive in.
Monitoring and Managing Symptoms
Since you can’t fully prevent fibroid growth during pregnancy, monitoring becomes the primary clinical strategy. Most providers will track fibroid size through ultrasound at regular intervals, paying particular attention to fibroids larger than 5 cm or those located in the lower part of the uterus near the cervix.
The most common fibroid complication during pregnancy is pain, often caused by a process called red degeneration, where a fibroid outgrows its blood supply and begins to break down internally. This can cause sudden, localized abdominal pain. The standard approach is rest, staying well hydrated, and acetaminophen for pain relief. Common anti-inflammatory medications should be used cautiously, especially in the third trimester, where prolonged use has been linked to complications for the baby.
Surgery to remove fibroids during pregnancy is rare and reserved for specific situations: a fibroid causing intractable pain (particularly one attached to the outer surface of the uterus by a stalk), rapid growth, or a large fibroid in the lower uterine segment that could obstruct delivery. When necessary, studies have shown that fibroid removal can be performed safely in the first and second trimesters.
Fibroids and Miscarriage Risk
One of the biggest fears for pregnant women with fibroids is miscarriage, and the evidence here is genuinely reassuring. A large prospective study that adjusted for key risk factors found no increased miscarriage risk associated with fibroids, regardless of their type, size, or total volume. Neither fibroids growing into the uterine cavity nor those embedded in the muscular wall showed a significant association with pregnancy loss. This held true even for the largest fibroids and highest total fibroid volumes studied.
What Happens After Delivery
Fibroid regression is common in the months following birth. Between early pregnancy and three to six months postpartum, most fibroids shrink substantially as hormone levels drop back to their pre-pregnancy baseline. In one study, the largest fibroid tracked showed a maximum volume reduction of nearly 89%. Women who delivered vaginally saw slightly higher rates of regression (74%) compared to those who had cesarean deliveries (68%), though the difference was not statistically significant.
For many women, the fibroids that caused concern during pregnancy become significantly smaller or clinically insignificant within half a year of delivery, often without any intervention at all.