Uterine Fibroids and Pregnancy

Can Fibroids Prevent Pregnancy?

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Uterine fibroids are present in up to 2.4% of women without any other obvious cause of infertility.¹ In such cases, submucosal fibroids (just underneath the uterine lining) and intramural fibroids (in the wall of the uterus) are thought to distort the shape of the uterine cavity. Intramural fibroids could also obstruct the fallopian tubes.¹⁻² In either case, these alterations to the uterus would interfere with sperm movement or possibly prevent egg implantation.¹ Subserosal fibroids (on the outside of the uterus) appear to have no effect on fertility.³

 

Women seeking treatment for uterine fibroids should understand the implications of treatment on their childbearing potential. Hysterectomy (removal of the uterus) completely eliminates a woman’s ability to bear children, while myomectomy and uterine fibroid embolization are fertility sparing treatments that can even improve fertility in some cases.³
 

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Can Fibroids Cause Miscarriage?

 

Whether or not uterine fibroids cause miscarriage has been a subject of debate amongst the medical community throughout the last two decades.

 

In the early 2000’s, fibroids were reported to increase risk of miscarriage by around 60%. Unfortunately, the studies that reported this finding were subject to some major scientific limitations - studies were retrospective with the majority of participants selected from prenatal care or ultrasonography clinics. In effect, these study populations were biased to include more women with a history of infertility, high risk pregnancy, and fibroids, and without adjusting for confounding factors, fibroids appeared to have a major influence on miscarriage rates. In the absence of better evidence, the American Society of Reproductive Medicine has endorsed fibroid intervention to reduce a woman’s chance of miscarriage by 50%.⁴

 

Between 2002 and 2012, a high quality prospective study followed the pregnancies of 5,512 women. The study assessed the presence, distribution, and types of fibroids in each of the study participants. Women with fibroids had a 30% increased risk of miscarriage compared to women without fibroids, and risk appeared greater in intramural (50% increase) and submucosal (70% increase) cases. However, when adjusting for other factors that are known to contribute to miscarriage - age, race, type 2 diabetes, BMI, miscarriage history, and prior termination of pregnancy - the researchers found that fibroids did not significantly increase the risk of miscarriage.⁴

 

These findings do not completely rule out a causal link between uterine fibroids and miscarriage, but they do emphasize that such a link may be a rare occurrence. In general, women should not seek fibroid treatment with the sole expectation of reducing miscarriage risk. Available fibroid treatments are intended to alleviate symptoms and not necessarily facilitate pregnancy.
 

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Effects of Fibroids on Pregnancy & Obstetrical Outcomes

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A number of obstetrical (child birth) outcomes have been studied in women with symptomatic uterine fibroids. Women with fibroids are more susceptible to: ⁵

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•  Preterm labor

•  Malpresentation (abnormal position of the fetus at time of delivery)

•  Placenta previa (placenta blocks the neck of the uterus)

•  Placental abruption (separation of placenta from the wall of the uterus)

•  Cesarean section

•  Postpartum bleeding / hemorrhage

•  Retained placenta