Fibroids and Pregnancy

Do Fibroids Interfere with Pregnancy?

Women who want to have children and discover they have uterine fibroid tumors immediately ask the question, "Will uterine fibroids interfere with pregnancy?" The question is a very legitimate one, considering that uterine fibroids typically develop during the childbearing years and it is estimated that three out of five women in this age group have fibroids.

Fibroids, generally speaking, do not interfere with conception or pregnancy. However, fibroids can affect fertility. Depending upon where they are located and the size of them, they may distort or block the fallopian tubes or interfere with the movement of sperm from the cervix to the tubes. Submucosal fibroids - the ones that grow on the inside walls of the uterus - may prevent implantation and the growth of the embryo. They may also cause miscarriages.

Some Fibroids Can Decrease Fertility

Submucosal fibroids that change the shape of the uterus, or intracavitary (within the uterine cavity) fibroids actually decrease fertility by about 70%. Conversely, when these types of uterine fibroids are removed, fertility increases by about 70%. Intramural (fibroids that are within the walls but don't change the shape of the uterus) and subserosal (outside the walls of the uterus) fibroids do not tend to decrease fertility and removal of them does not affect an increase in fertility.

Miscarriage and Fibroids

A miscarriage can be the result of fibroid tumors. Once the egg is fertilized, it comes down the fallopian tube and into the uterus where it implants in the tissue of the womb. If there is a submucosal fibroid close by, it can thin the uterine lining and decrease the blood supply available for the embryo. The fibroid can also cause inflammation in the lining of the uterus. The fetus cannot develop properly and the result may be a miscarriage. However, a subsequent pregnancy my implant in another location and the pregnancy may proceed without incident. If there has been a miscarriage and a fibroid is found, it should be removed.

Pregnant With Fibroids

Although most fibroids do not grow during pregnancy, pregnancy can have an unpredictable effect upon these tumors. The individual genetic changes in a fibroid during pregnancy and the type and amount of growth factors that are available in the blood can affect the growth of a fibroid tumor. Only about one-third of women experience fibroids increasing in size during pregnancy and the tumors almost always shrink after delivery.

Most studies show the risks of premature delivery, fetal growth problems, fetal abnormalities, problems with the placenta or heavy bleeding after the baby is born, are no different than those risks to women without fibroids. However, sometimes a fibroid can interfere with delivery in which case a cesarean delivery is performed.

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