Linda Carroll | In most cases, fibroids won't cause a problem with pregnancy according to experts | (Today Health & Wellness)

Often, the first time a pregnant woman learns she has a fibroid is during her initial routine ultrasound. That's because fibroids usually don't cause symptoms. But they are quite common—more than 70 percent of women have them.

In most cases, fibroids won't cause a problem with the pregnancy, experts say.

"Common as they are, complications during pregnancy are relatively unusual," says Dr. Philip D. Orons, a professor of radiology and chief of interventional radiology at the Magee-Womens Hospital of the University of Pittsburgh Medical Center. "The most common problem is symptoms in the mom, which can include pain, nausea, fever, vomiting and occasionally elevations of the white blood cells."

Uterine fibroids are abnormal, noncancerous growths that develop on a woman's uterus. Their cause is unclear, but they may be related to hormones or run in families. Once a woman is pregnant, fibroids can't be removed because the uterus is prone to bleed more than normally. So women have to live with them until after the baby is born.

Related: FDA warns against fibroid removing device in this Novemebr 2014 article on NBCNews.

Although problems associated with fibroids are rare, it's still important to be aware of the possible complications.

Pain

Fibroids larger than 2 inches are more likely to increase in size during pregnancy since their growth is driven by the hormones progesterone and estrogen. When growth is rapid, sometimes the central portion of the fibroid can degenerate and this can cause pain, Orons says.

Another scenario is when a fibroid is growing outside the uterus on a stalk.

"You can have a torsion of the stalk and that can cause pretty severe pain during pregnancy," Orons says.

Generally doctors will treat the pain with acetaminophen. If that doesn't work they may prescribe a short course of narcotics or NSAIDs like ibuprofen, Orons says, although "NSAIDs should only be used before 32 weeks gestation because the use of these types of medications later in the third trimester has been associated with developmental defects. Rarely, patients need to be hospitalized for intravenous pain control."

Complications during pregnancy:

• Comprised blood supply: "If the fibroid is located right by the placenta, it can affect the blood supply to the fetus," says Dr. Stacey Scheib, director of minimally invasive gynecology at the Johns Hopkins Medicine and director of the Hopkins Multidisciplinary Fibroid Center. "Then sometimes the baby may be born a little on the small side and there can be complications, including difficulty breathing, problems maintaining weight and body temperature." If the blood supply is severely compromised and there's a drop in weight, doctors may need to deliver sooner rather than later.

• Risk of preterm birth or premature rupture of the membranes: A growing fibroid can increase the likelihood that the birth will be premature, or that the woman's water will break before the baby is ready to be born, Scheib says.

Complications during delivery:

• Baby's position adversely affected: Depending on the location and orientation of the fibroid, the baby can end up in either a transverse or breech position, Scheib says. That may necessitate a C-section.

• Fibroid can make vaginal delivery impossible: If the fibroid is in a lower part of the uterus near the cervix, it can obstruct delivery, Scheib says. In that case, a C-section will be required.

• Fibroid may lead to hysterectomy: Sometimes the fibroid will need to be removed in order for the obstetrician to close the uterus up, Scheib says. "Those situations are rare but because of them, there is a slightly increased risk of hysterectomy at the time of the C-section delivery," she adds.

Ultimately, women should take comfort in the knowledge that all of these pregnancy complications are very rare, both Scheib and Orons say.