Potential risk factors associated with subtypes of uterine leiomyomata.

Objective: To compare potential risk factors for uterine leiomyomata (UL) subtypes among premenopausal African American and Caucasian women.

Methods: This cross-sectional study included 986 premenopausal women, aged 35 to 49 years old, from the National Institute of Environmental Health Sciences (NIEHS) Uterine Fibroid Study (UFS). Uterine leiomyomata were subtyped as submucosal, intramural/subserosal, and diffuse, based on ultrasound examinations.

Results: For both ethnic groups, age, age at menarche, body mass index, and current physical activity had similar associations across the 3 UL subtypes. Inverse associations with pregnancies after age 24 appeared to be stronger for the submucosal subtype. Current smoking was associated only with diffuse UL (adjusted odds ratio [aOR] = 1.97, 95% CI: 1.11, 3.51 in African Americans, aOR = 3.00, 95% CI: 1.07, 8.38 in Caucasians).

Conclusions: Although the 2 focal UL subtypes had similar risk factor profiles, the diffuse UL subtype appeared to have a distinctive risk profile with regard to current smoking. Further study of the diffuse heterogeneity seen with uterine ultrasound is needed.