Effect of Uterine Fibroids on Pregnancy

Most women, whether knowingly or unknowingly, develop uterine fibroids at some point in their lives. It is estimated at three out of four women experience them during their lifetime, but since they are often miniscule, they go unnoticed. Uterine fibroids are non-malignant tumors that grow in or on the uterus and are most frequently found in women of childbearing age. Overall, they aren't associated with cancer and are quite manageable.

What Affects Uterine Fibroid Growth?

The cause of uterine fibroids is still unknown; however, they do appear to rely upon estrogen for growth. When women have gone through menopause and estrogen is gone, fibroids disappear, and they don't develop until after puberty. These two factors alone support the idea of estrogen dependence for growth of uterine fibroids.

There are other factors that may have a bearing upon uterine fibroid growth:

· Pregnancy - it appears that women who have had children tend to have fewer if any fibroids

· Early menstruation can kick-start fibroids - likely due to the early onset of estrogen

· Uterine fibroids are less prevalent when birth control pills are taken - again the estrogen connection

· A family history of uterine fibroids can indicate the possibility of having them

As a rule, women with fibroid tumors do not have trouble becoming pregnant even though one out of every 15 women suffering with infertility has fibroids. However, the fibroids are usually unobtrusive and are only responsible for about two or three percent of infertility cases. They are implicated when:

· Fibroids block one or both of the fallopian tubes which may prevent sperm getting to the egg to fertilize it

· Fibroids may entirely fill the uterine cavity in which case there is no room for implantation of a fertilized egg

How Do Uterine Fibroids Affect Pregnancy?

Fibroids may cause complications in a pregnancy, although often a woman with fibroids can go through a pregnancy with only minor complications, if any at all. In extreme cases, fibroids that bulge into the uterine cavity, called submucosal fibroids, or those that are actually inside the uterus, called intracavitary, may cause miscarriage. In pregnancy, a fertilized egg makes it way down the fallopian tube and into the uterine cavity where it implants into the lining of the uterine wall. If a submucosal fibroid is in the vicinity it can cause the lining of the uterus to thin out and deplete the blood supply to the embryo. Inflammation may also occur in the lining above. As a result, the embryo is unable to develop and spontaneously aborts. It is possible that in a subsequent pregnancy the egg will implant in another location and the pregnancy will be fine. If a miscarriage occurs and a fibroid is found, it's best to just have it removed.


Other Effects of Uterine Fibroids on Pregnancy

There are other complications that can arise from fibroids in a pregnancy:

· Premature labor can be triggered by fibroids.

· The baby may be unable to be in the right position for delivery due to obstruction by a fibroid. If the fibroid is growing close to the cervix and is large enough, it can block the exit of the baby from the womb. This may necessitate a cesarean section to deliver the baby.

· Placental abruption occurs in one in 200 births. When the placenta separates from the uterus too soon, before the baby is born, it can cut off the baby's supply of nutrients and blood and can, in certain situations, be life threatening. Fibroids contribute to placental abruption.

· Postpartum hemorrhage occurs after childbirth. The uterine contractions that control bleeding are obstructed by fibroids and the squeezing of the contractions is not hard enough to control the bleeding. In rare occasions a blood transfusion may be necessary.

The effect of pregnancy upon fibroids is generally unpredictable; however, most do not grow during pregnancy. They almost never hurt the growing baby, although they may cause some crowding if they grow. The size of fibroids is variable during pregnancy with some remaining the same size, some shrinking and others growing. Ultrasound imaging helps the doctor keep an eye on both baby and tumor. Should anything develop that would pose a danger, it will be addressed quickly and effectively.

Learn more about uterine fibroids, the various types and treatments in our article in this section.

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