Importance: Uterine fibroids are an understudied condition, with earlier onset in Black than White women. Prior studies of the importance of family history on fibroid development are limited by reliance on hospital-based participant selection, poorly defined measures of family history, and nonsystematic fibroid assessment.

Objective: To examine whether family history is a risk factor for fibroid development using prospective ultrasonography data to identify incident fibroids and measure fibroid growth and standardized methods to ascertain family history.

Design, setting, and participants: This prospective community cohort of Black and African American women from the Detroit, Michigan, area was conducted from January 1, 2010, to December 31, 2018, using 4 standardized ultrasonographic examinations during 5 years to detect fibroids 0.5 cm or larger in diameter and measure fibroid growth. Data analysis was performed between May 2022 and January 2024.

Exposures: Maternal fibroid history data were gathered directly from participants' mothers when possible (1425/1628 [88%]), and 2 exposure variables were created: maternal history of fibroids (diagnosed vs not diagnosed) and age at maternal fibroid diagnosis (20-29, 30-39, or ≥40 years vs not diagnosed).

Main outcomes and measures: Fibroid incidence was assessed using multivariable Cox proportional hazards regression models; fibroid growth was calculated as change in log-volume per 18 months for fibroids matched at successive ultrasonograms.

Results: A total of 1610 self-identified Black and/or African American women aged 23 to 35 years (mean [SD] age, 29.2 [3.4] years) with no prior clinical diagnosis of fibroids at enrollment were available for analysis. Of 1187 fibroid-free participants at enrollment, 442 (37%) had mothers who were diagnosed with fibroids. Compared with participants without a maternal history of fibroids, those reporting maternal history had an adjusted hazard ratio (AHR) of 1.21 (95% CI, 0.96-1.52). Risk was strongest in those whose mothers were diagnosed at a younger age (20-29 years: AHR, 1.56; 95% CI, 1.11-2.21; 30-39 years: AHR, 1.03; 95% CI, 0.71-1.49; ≥40 years: AHR, 1.11; 95% CI, 0.81-1.52; P = .053 for trend). Fibroid growth rates were higher when mothers were diagnosed with fibroids vs not diagnosed (8.0% increased growth; 95% CI, -1.2% to 18.0%).

Conclusions and relevance: In this prospective cohort study, results supported maternal history of fibroids as a risk factor for incident fibroids, especially when mothers were diagnosed at a younger age. Maternal history was also associated with increased fibroid growth. Asking patients about their family history of fibroids could encourage patient self-advocacy and inform care.