I have a small fibroid on my uterus. Should I be worried?

Q: I'm hoping to get pregnant and just found out I have a small fibroid in my uterus. My doctor said not to be worried, but I am. What should I do? 

A: Get a second opinion. While some experts believe uterine fibroids, which are noncancerous tumors, do not cause miscarriage, others say they can. "The key is a fibroid's location and size," says William P. Hummel, M.D., a reproductive endocrinologist specializing in miscarriage at the San Diego Fertility Center. The closer it is to the center of the uterus, where a fetus is likely to implant, the more likely it is to cause problems. As for size, any fibroid greater than 5 centimeters—about 2 inches—can be problematic. "A fibroid of this size is very vascular [has a lot of blood vessels]," Hummel explains. "A large fibroid shunts blood flow away from the uterus to fuel its own growth."
Although your fibroid may be small now, that could change when you become pregnant, making some preventive medicine even more important. "During pregnancy, fibroid growth tends to accelerate," Hummel says. "A borderline significant fibroid can grow to the point where it jeopardizes the pregnancy."