Fibroids and Infertility – New Information!
It is generally agreed the while uterine fibroids are very common; they are usually not associated with infertility. Size and location are the two main characteristics, which determine if fibroids may be implicated in infertility or increased risk of miscarriage. These benign tumors have long been classified according to their location. Fibroids located within the uterine cavity are referred as submucous fibroids. If located within the uterine wall fibroids are classified as intramural, and when these tumors are positioned on the outer surface of the uterus, they are termed subserous.
When fibroids are located within the uterine cavity (submucous) most agree that they interfere with normal embryo implantation and are associated with both infertility and increased risks of miscarriage. Sub-serous fibroids and have traditionally not been associated with infertility. The impact of intra-mural fibroids on fertility is more complicated and is dictated by size and location of fibroids with respect to the uterine cavity. Fibroids that have reached a diameter of 5 centimeters or greater and are located within the uterine wall (intramural) are associated with infertility and premature labor. In addition, fibroids smaller than 5 centimeters in diameter that distort the uterine cavity are implicated in decreased fertility, increased miscarriage rates, and increased incidence of pre-term labor. Although many patients conceive and carry successfully with fibroids of this size, studies have demonstrated that infertility and obstetrical complications such as pre-term labor are more common in this group of patients.
Many have questioned smaller intramural fibroids might be problematic, especially if they are numerous, above a certain size threshold, or located close to the uterine cavity and there are few well designed large studies looking at this question. A recent study published by Yan et al. in Fertility and Sterility, March 2014, addressed this question in patients who had fibroids and underwent in-vitro-fertilization. The study was retrospective and looked at a large number of patients (249) with uterine fibroids of various sizes and locations. One of the findings of their study was that when the single largest intramural fibroid was 2.85cm or larger, the delivery rate was significantly lower than matched controls who had no fibroids. It is important to point out that this study did not address the question of whether removal of the fibroids in this group of patients would improve the delivery rate. A prospective study looking at patients whose largest intramural fibroid is greater than 2.85 cm. in diameter, comparing a surgically treated group versus a non-treated group is needed.
The Yan et al. study also looked at outcomes in patients with multiple intramural fibroids and found that clinical pregnancy rates and delivery rates were similar for patients with multiple intra-mural fibroids compared with matched patients with no fibroids.
An additional finding of this study was that intramural fibroids near the uterine lining but not distorting it did not have a statistically significant impact on pregnancy rates.
Importantly, these authors studied results of IVF with intra-cytoplasmic sperm injection (ICSI) in 249 patients with fibroids and compared their outcomes to a group of carefully matched controls that did not have fibroids, and found very little differences in terms of clinical pregnancy rates, delivery rates, and miscarriage rates.
This study, while not answering all of our questions concerning fibroids and reproduction, does provide valuable information for patients with fibroids who are preparing for IVF.