Occasionally, fibroids exert pressure on the ureters and can cause kidney dysfunction. The size of the enlarged uterus is often compared to the size of a pregnant uterus, as in a 12-week pregnant uterus. Causes of Uterine Fibroids Researchers have been able to identify the influence of hormones in the growth of fibroids, but have yet to determine conclusively what causes them. Other hormones, such as growth hormone and prolactin, are now also thought to be important. The initiating event that triggers the onset of fibroid growth is still unknown, but we do know there is a strong inherited component.
Evidence suggests a higher incidence of uterine fibroids in black women than in white women.
Also, studies on twins have demonstrated a higher incidence of hysterectomy in identical female twins than in fraternal twins. Few studies have examined the impact of fibroids on reproductive dysfunction, but generally clinicians acknowledge that fibroids distorting the uterine cavity can affect the ability to conceive and the outcome of pregnancy. The presence of uterine fibroids is associated with premature labor, repeat miscarriage, infertility, fetal malpresentations, excessive postpartum bleeding and other complications of labor. Large uterine fibroids blocking the birth canal may necessitate delivery by cesarean section. Submucosal fibroids, those located under the innermost layer of the uterus, can distort the uterine lining and may be the most significant cause of reproductive problems from fibroids.