Fibroids are related to infertility. There is a general agreement that submucosal leiomyomas negatively affect fertility, when compared to women without fibroids. Submucosal fibroids have a statistically significant negative effect on clinical pregnancy rates as reported by a meta-analysis of 13 studies, the study also showed a lesser extent of intramural fibroids on clinical pregnancy rates. About delivery rates, submucosal and intramural fibroids showed a negative impact. On the contrary, subserosal myomas did not show any effect on clinical pregnancy rates and delivery rates. Thus, submucous and intramural LMs are more involved for sterility and infertility cases due to alteration of uterine cavity and contractility, while subserosal fibroids do not seem to generate any obvious fertility issue.
However, it is still not entirely clear how fibroids may cause infertility. The possible mechanism of impairing fertility also depends on the localization of the fibroid. As mentioned above, the type of fibroids most commonly associated with reduced fertility are submucosal fibroids. It is possible that these fibroids divert the blood flow from the overlying region of endometrium (uterine lining), which impairs its growth and proper function, and may prevent the embryo from successfully implanting.
A much more rare cause of reduced fertility are subserosal fibroids. Depending on their localization, large subserosal fibroids can obstruct the opening of the uterine tubes into the uterine cavity, preventing the embryo from entering the cavity and implanting. Very large or multiple fibroids that alter the overall shape of uterine cavity may be also associated with adverse pregnancy outcomes, such as miscarriage or abnormal fetal presentation, as the deformed uterus is not able to properly accomodate the developing fetus.