Fibroids can affect fertility, but the impact depends heavily on where they grow and how large they are. Most women with fibroids conceive without difficulty. The fibroids most likely to cause problems are those that distort the inner cavity of the uterus, where an embryo needs to implant. Fibroids growing on the outer surface of the uterus generally have little to no effect on conception.
Why Location Matters More Than Size
The uterus has three layers, and fibroids can grow in any of them. Submucosal fibroids, which bulge into the uterine cavity, have the clearest link to reduced fertility. They physically distort the space where an embryo implants and can interfere with sperm transport. Intramural fibroids grow within the muscular wall of the uterus. When they’re large enough to push into and reshape the cavity, they behave similarly to submucosal fibroids, lowering pregnancy, implantation, and delivery rates. Subserosal fibroids, which grow outward from the uterus toward the abdomen, are the least concerning for fertility.
Even intramural fibroids that don’t visibly distort the cavity still appear to reduce fertility. A meta-analysis of over 6,200 IVF cycles found that women with these non-cavity-distorting intramural fibroids had an 18 to 19% lower live birth rate compared to women without fibroids. In first IVF cycles specifically, the reduction was roughly 25%. Miscarriage rates were also higher.
How Fibroids Interfere With Implantation
Beyond the mechanical distortion, fibroids alter the biology of the uterine lining itself. The endometrium prepares for pregnancy each cycle by ramping up certain genes that make it receptive to an embryo. Two of the most important are transcription factors that peak during the implantation window. In women with fibroids, the expression of these genes is measurably decreased, which may explain why even fibroids that don’t obviously reshape the cavity still lower pregnancy rates.
Fibroids also change blood flow patterns in the uterus and can create a low-grade inflammatory environment. This combination of altered gene expression, disrupted blood supply, and inflammation makes the lining less hospitable to an embryo, even when ovulation and fertilization are happening normally.
Size Thresholds That Matter
Fibroids smaller than 5 centimeters (about 2 inches) are generally not associated with significant increases in adverse outcomes. Once they exceed 5 centimeters, pregnancy risks begin to climb. A study of 651 pregnancies found that fibroids between 5 and 10 centimeters roughly doubled the odds of complications, while those larger than 10 centimeters nearly quadrupled the risk. The American Society for Reproductive Medicine has actively debated whether intramural fibroids larger than 3 to 4 centimeters should be surgically removed before IVF, reflecting the lack of a single agreed-upon cutoff.
Number matters too. The negative effects on IVF outcomes increase with both increasing fibroid size and increasing number of fibroids.
Fibroids and Pregnancy Complications
Getting pregnant is only part of the picture. Women with fibroids face a higher rate of preterm birth: 11.6% compared to 9.0% in women without fibroids. The earlier the preterm birth, the stronger the association. The risk of delivering before 34 weeks was nearly doubled, and the risk of delivering before 28 weeks was more than doubled. Fibroids can also increase the likelihood of placental abruption, fetal growth restriction, and cesarean delivery. These risks are most pronounced with larger fibroids.
Surgical Removal to Improve Fertility
Myomectomy, the surgical removal of fibroids while preserving the uterus, is the most common fertility-focused treatment. Post-surgical fertility rates are estimated at 54 to 56%. For submucosal fibroids, removal is widely recommended before attempting conception or IVF, since the evidence that they impair implantation is strong. For intramural fibroids, the decision is more nuanced and depends on size, location relative to the cavity, and whether there are other fertility factors at play.
After a laparoscopic myomectomy, most reproductive specialists recommend waiting 3 to 6 months before trying to conceive, giving the uterine wall time to heal. Some clinicians advise waiting 6 to 12 months, particularly after open abdominal surgery or removal of deep intramural fibroids. No major gynecological association has issued formal guidelines on the exact interval, so recommendations vary between practitioners.
Why Uterine Artery Embolization Is Risky for Fertility
Uterine artery embolization (UAE) shrinks fibroids by cutting off their blood supply. It’s effective for symptom relief, but it carries real concerns for women who want to become pregnant. A randomized trial comparing UAE to myomectomy found the relative risk of infertility after UAE was 2.2 times higher. Miscarriage rates after UAE were also significantly elevated: 64% in one study, compared to 23% after myomectomy.
Pregnancies after UAE show higher rates of preterm delivery, cesarean section, and postpartum hemorrhage compared to pregnancies after myomectomy. There is also the possibility of non-target embolization, where particles intended for the uterine arteries reach the ovaries through connecting blood vessels, potentially reducing ovarian reserve. In one study, 4 out of 163 patients developed premature menopause after UAE, all over the age of 45. For women planning future pregnancies, myomectomy is generally preferred over UAE.
What This Means for Your Next Steps
If you have fibroids and are trying to conceive, the most important thing to find out is where your fibroids are located and whether they distort the uterine cavity. An ultrasound can identify fibroid position, but a saline infusion sonogram or MRI gives a clearer picture of how fibroids relate to the inner cavity. Small fibroids on the outer wall of the uterus are unlikely to be the reason you’re not getting pregnant. A submucosal fibroid, or a large intramural fibroid pressing into the cavity, is a different situation entirely and one where treatment before conception can meaningfully improve your chances.