A: Fibroids, also called myomas, are benign collections of muscle and connective tissue that can grow within the wall of the uterus. They are quite common and are found in 30 to 40% of women over 30 years old. Fibroids can be located on the outside of the uterus, within the wall of the uterus or into the cavity of the uterus.

Fibroids grow in response to the extra hormones and blood flow of pregnancy. Their size and location will largely determine what kind of impact they have on your pregnancy. Fibroids that grow on the outside of the uterus will sometimes cause pain during a pregnancy but are unlikely to affect your fetus. A large fibroid that grows into the cavity of the uterus could possibly compromise your baby's space for growing, cause your baby to lie in an abnormal position or block the passageway for a vaginal delivery.

Having fibroids increases your risk of preterm labor, so learn the common signs of preterm labor: abdominal cramping, uterine tightening, low back pain, pelvic pressure and unusual vaginal discharge. Your midwife or doctor could check your cervix at your prenatal exams to ensure that it isn't thinning or opening early.

A cesarean section is recommended if your prior surgery, called a myomectomy, required a deep incision through the entire thickness of the uterine wall. Theoretically, your uterine scar might be vulnerable to the stresses of hard labor, putting you at an increased risk of a uterine rupture. To avoid any chance of this emergency, doctors perform cesarean sections rather than permitting a lengthy labor in women who have had a deep myomectomy. Cesarean sections are also needed if large fibroids are located close to the cervix, obstructing the birth canal and preventing a vaginal delivery.

Most babies grow quite nicely despite the presence of fibroids, and the vast majority of my patients with fibroids have no complications with pregnancy. Your doctor will likely order ultrasounds during your pregnancy to visualize the size and location of your fibroids and to monitor the growth of your baby. Speak to your doctor about these results and learn if any special interventions are recommended in your particular situation.