women with uterine fibroids will have normal pregnancy outcomes. In cases of intercurrent uterine fibroids in infertility, a fibroid is typically located in a submucosal position and it is thought that this location may interfere with the function of the lining and the ability of the embryo to implant. Risk factors Some risk factors associated with the development of uterine fibroids are modifiable. Fibroids are more common in obese women. Fibroids are dependent on estrogen and progesterone to grow and therefore relevant only during the reproductive years. Diet Diets high in fruits and vegetables tend to lower the risk of developing fibroids. Fibers, vitamin A, C and E, phytoestrogens, carotenoids, meat, fish, and dairy products are of unclear effect. Normal dietary levels of vitamin D may reduce the risk of developing fibroids. Genetics Fifty percent of uterine fibroids demonstrate a genetic abnormality. Often a translocation is found on some chromosomes. Fibroids are partly genetic. If a mother had fibroids, risk in the daughter is about three times higher than average. Black women have a 3–9 times increased chance of developing uterine fibroids than white women. Only a few specific genes or cytogenetic deviations are associated with fibroids. 80–85% of fibroids have a mutation in the mediator complex subunit 12 (MED12) gene. Familial leiomyomata A syndrome (Reed's syndrome) that causes uterine leiomyomata along with cutaneous leiomyomata and renal cell cancer has been reported. This is associated with a mutation in the gene that produces the enzyme fumarate hydratase, located on the long arm of chromosome 1 (1q42.3-43). Inheritance is autosomal dominant. Pathophysiology Fibroids are a type of uterine leiomyoma. Fibroids grossly appear as round, well circumscribed (but not encapsulated), solid nodules that are white or tan, and show whorled appearance on histological section. The size varies, from microscopic to lesions of considerable size. Typically lesions the size of a grapefruit or bigger are felt by the patient herself through the abdominal wall. Microscopically, tumor cells resemble normal cells (elongated, spindle-shaped, with a cigar-shaped nucleus) and form bundles with different directions (whorled). These cells are uniform in size and shape, with scarce mitoses. There are three benign variants: bizarre (atypical); cellular; and mitotically active. The appearance of prominent nucleoli with peri-nucleolar halos should alert the pathologist to investigate the possibility of the extremely rare hereditary leiomyomatosis and renal cell cancer (Reed) syndrome. Location and classification Growth and location are the main factors