Do Fibroids Affect Pregnancy?

Most women with fibroids have no more trouble becoming pregnant than women who do not have fibroids, and their risk of a bad pregnancy outcome is no higher.

About 1 in every 15 women with infertility has fibroids, but the fibroids are usually innocent bystanders: They cause only 2% to 3% of cases of infertility. Fibroids that block one or both of the fallopian tubes may prevent sperm from fertilizing an egg. Fibroids that fill the uterine cavity may block implantation of a newly fertilized egg.

Fibroids-especially those located in the cavity of the uterus-may increase the chance of a miscarriage or may cause a woman to go into labor before her due date (premature labor). Fibroids may also increase the chance that the baby is not positioned to come out headfirst. This can increase the need for cesarean section. Rarely, fibroids can cause complications of pregnancy called placental abruption and postpartum hemorrhage.

What Is Placental Abruption?

After childbirth, the afterbirth (placenta) separates from the uterus. Placental abruption occurs when the placenta separates from the uterus too quickly (i.e., before the baby is born). It occurs in one of every 200 pregnancies.

In addition to causing vaginal bleeding and pain, placental abruption can cut off the baby's supply of nutrients and blood. In severe cases, this can threaten the baby's life.

What Is Postpartum Hemorrhage?

Normally, the afterbirth (placenta) separates from the uterus after childbirth. When this happens, the muscle in the uterus usually squeezes the uterus to help stop bleeding. If a fibroid is present, the squeezing of the muscle in the uterus may be less effective and the woman may have more bleeding. Rarely, the blood loss may be significant and the woman may need medications, surgery, and/or a blood transfusion.

Some fibroids grow during pregnancy, but some remain the same size and others shrink.