Will my fibroids prevent me from getting pregnant?
A recent PFC study can help answer that question.

Every complete infertility evaluation includes a thorough evaluation of the uterus, where embryo implantation is expected to occur. At Pacific Fertility Center we typically start with a vaginal ultrasound to evaluate for the presence of fibroids (benign growths of the muscle layer), polyps (benign growths of the lining of the uterus), measure the lining thickness of the uterus and observe the uterine lining pattern. If uterine abnormalities are noted, a saline hysterogram (saline ultrasound) or hysteroscopy (visualizing the uterine cavity with a thin telescope) may be recommended.

Fibroids (uterine leiomyomas) are present in 20-40% of reproductive age women. The location of the fibroid(s), relative to the lining of the uterus, is important in determining if it will impact chances of pregnancy. Fibroids which distort the uterine lining and cavity are known to decrease pregnancy rates for patients undergoing fertility treatment. Only about 5% of fibroids directly distort the uterine cavity. The influence of fibroids which do not distort the uterine cavity has remained controversial.

To best determine if non-distorting fibroids also may have an impact on fertility treatment, requires the analysis of a large number of fertility cycles following patients who have non-distorting fibroids, and patients who have no fibroids. Most studies have small numbers of observed cycles, making statistical analysis difficult. One strategy for circumventing this problem, and gathering enough treatment cycles to draw meaningful statistics, is to have large IVF centers collaborate and “pool” data. This type of study is called a multi-center study.

Pacific Fertility Center (PFC) and the University of California San Francisco (UCSF) IVF centers collaborated in just such a study; gathering data on past treatment cycles of egg donor recipients with non-cavity distorting fibroids and without fibroids. Analysis of pregnancy (PR) and implantation (IR) rates were assessed. A total of 369 cycles were analyzed, of which 94 were for patients with fibroids. All recipients underwent their first oocyte donor cycle, and a fresh embryo transfer. Any uterine abnormalities other than non-distorting fibroids were excluded from the study analysis. The primary outcome measure was a clinical pregnancy. Implantation rate was a secondary outcome of the study. We also analyzed to see if the fibroid location: subserosal (growing towards the outside of the uterus) versus intramural (confined to the muscle layer) or if the fibroid diameter impacts PR and IR, as well as miscarriage and ectopic rates.

The following results were revealed.

The clinical pregnancy rate (PR) was not different between the two groups (no fibroids vs fibroids) (54% vs 47%). The implantation rate (IR) was also similar between the groups (38% vs 36%). Miscarriage rates were similar (9% vs 15%). Ectopic pregnancy (which is typically a rare outcome) showed results of 1% vs 4%, which also was not statistically significant. Location and diameter of fibroids did not show a significant impact on PR.

When screening ultrasounds identify fibroids, “treatment” of these lesions is tempting to both providers and patients, especially in cases of unexplained infertility. Our data suggest that there is inadequate evidence to conclude that fibroids which do not distort the uterine cavity have a significant effect on clinical pregnancy rates (PR) in patients undergoing IVF. Thus, there is inadequate evidence to support myomectomy for patients with non-distorting fibroids. Myomectomy may unnecessarily place the patient at risk of delayed treatment, as well as possible surgical morbidity. It is also unknown whether surgery itself may have a negative impact on pregnancy outcome- though our data did not show a lower PR in patients who had past myomectomies.

Future collaborative studies will investigate whether the distance of the closest fibroid to the uterine lining may impact PR and IR. Fibroid volume will also be investigated. These studies are currently in the design phase.

Isabelle Ryan, MD

“The effects of fibroids without cavity involvement on ART outcomes independent of ovarian age”, PC Klasky, DE Lane, IP Ryan, VY Fujimoto, Hum Reprod Advance Access, published September 22, 2006.

Q.
I sought our physician’s opinion about how my fibroids might impact our desire to get pregnant. Eight doctor opinions later, we are no closer to a decision. About half of the experts advise surgical removal; and the other half tell us to try to get pregnant despite them. Why is the medical community divided on this?

A.
Fibroid(s) of the uterus, also known as leiomyomas or just myomas, are benign growths that may be located on the exterior of or within the muscle layer of the uterus, or may be growing within the lining of the uterus. For the vast majority of women, fibroids do not cause significant health problems.

A few women who desire pregnancy may need to have their fibroids removed (myomectomy) prior to conceiving if the fibroids are very large (greater than 6 cm) and/or if they impinge upon and distort the uterine cavity.

Various surgical approaches to removal are further described on PFC’s web site, along with a more in depth summary of the factors that our physicians consider when counseling a patient to undergo a myomectomy.

You probably received different opinions because the impact of fibroids as related to pregnancy chances depends on the size and location of the fibroids. Other issues to consider are that fibroids are dependent on estrogen to grow, and high levels of estrogen produced during pregnancy can lead to rapid growth of the fibroid(s). If the fibroid is on the outer surface of the uterus, this may present little problem. If the fibroid is located within the uterus muscle wall or nearer the uterine cavity where the fetus is growing, a patient may be at higher risk for various pregnancy complications (miscarriage, preterm labor…).

In rare cases, the fibroid may grow so rapidly during pregnancy that it outgrows its blood supply and starts degenerating, which can be painful and sometimes lead to pregnancy complications. Also uncommon but of significance is the fact that some fibroids may block the lower portion of the uterus, prohibiting the baby’s head to descend into the birth canal, making cesarean delivery necessary. However, it is important to keep in mind that the majority of patients with fibroids experience no problems during pregnancy.

What is the impact of fibroids on pregnancy chances? It is unclear that there is any negative impact, if the fibroids are small and not growing within or distorting the uterine cavity.