Myomas can distort the uterus, making it enlarged and elongated and altering its contour and surface area. They can also obstruct the tubal ostia and cervical canal, and displace the cervix in the vagina. Such acquired abnormalities can impair migration of sperm, ovum, or embryo, and negatively impact implantation. Studies suggest that the presence of myomas may cause dysfunctional and altered uterine contractility, which could hinder gamete transport and embryo implantation. In addition, myomas can adversely affect the overlying endometrium, creating endometrial vascular disturbances, inflammation, ulceration, thinning, and atrophy, and an altered biochemical environment that can impair implantation. With myomas, location is arguably the most important factor, as submucosal myomas are most commonly implicated in impaired fertility, followed by intramural and subserosal myomas. Most studies of submucosal myomas and infertility indicate that this particular location negatively impacts fertility, which improves after resection.
Reviewing the evidence Several studies have evaluated the effect of intramural fibroids on in vitro fertilization (IVF). One prospective case–control study compared women with intramural myomas smaller than 5 cm to matched controls who had normal endometrial cavities on hysterosalpingogram, all of whom underwent IVF.1 The authors hypothesized that smaller intramural or subserosal myomas in a normal endometrial cavity would not affect implantation or miscarriage. They found no statistically significant differences between the two groups, although the women with myomas had lower rates of implantation (13.6% vs. 20.2%), pregnancy rates (34.4% vs. 47.5%), and delivery (22.9% vs. 37.7%) and higher rates of miscarriage (33.3% vs. 20.7%). The study likely was underpowered for detecting statistically significant differences between the groups.
Surrey and colleagues conducted a retrospective case–control study of patients with intramural myomas and normal endometrial cavities undergoing IVF.3 The women with the tumors and normal endometrial cavities had lower rates of implantation (21.4% vs. 33.9%) compared to age-matched controls. A trend toward lower clinical pregnancy and live birth rates also was seen in that group. On the other hand, live birth rates were not affected by the presence of intramural myomas with a hysteroscopically normal cavity.
A review published in 2003 investigated the impact of intramural myomas on IVF outcomes.4 The author concluded that myomas immediately adjacent to or impinging on the endometrial cavity can negatively impact IVF, and in these cases, myomectomy may be indicated.