Prevalence in pregnancy

Fibroids greater than 0.5 cm are found in about 10% of women.  Most of these are not clinically significant.

What happens to fibroids during pregnancy?

60-70% of fibroids remain unchanged during pregnancy.  Only a small percentage grow in size and a large percentage of these shrink or even disappear.  Most fibroids will shrink back to their normal size following delivery.

Do fibroids increase the risk of miscarriage?

There has been some conflicting research regarding this.  More recently, however, a large study has shown over a 50% increase risk of miscarriage in women with fibroids.  In general, only fibroids that distort the shape of the uterus or impinge on the uterine cavity increase the risk of miscarriage.  Fibroids that are small and/or located deep in the uterus or on the outside of the uterine wall are unlikely to cause miscarriage or infertility.

Complications during  pregnancy

It is important to keep in mind that, even though 10 % of pregnant women have fibroids, the risk of complications is very low. Some possible complications that may occur are: early first trimester bleeding, placental abruption (separation of placenta from uterine wall), preterm labor and fibroid degeneration.  Fibroids rarely may cause problems with delivery i.e.:  obstruction the passage of the baby into the vagina and an increased chance of breech presentation. C-section delivery rate is more than twice that of women with no fibroids.