Women’s Health
Oral contraceptives and uterine fibroid development in a prospective ultrasound study of Black and African American women Christine Langton* Christine Langton Donna Baird Quaker Harmon
Uterine fibroids are highly prevalent benign tumors of the uterine muscle. Fibroids are the leading indication for hysterectomy, and Black and African American women are disproportionally burdened. Fibroids are dependent on estrogen and progesterone and oral contraceptives (OCs) manipulate these hormone levels. Studies examining the relationship between OCs and fibroids have had mixed results, and none utilized ultrasounds to prospectively assess fibroid incidence and growth.
We evaluated the association between OCs and fibroid development among 1,610 self-identified Black/African American women aged 23-35 years in the Study of Environment, Lifestyle & Fibroids. A standardized ultrasound examination was conducted at 4 clinic visits over 5 years to detect fibroids ≥0.5 cm in diameter. OC use was assessed at each visit and age at first use was reported at enrollment and derived thereafter. We used Cox regression to estimate hazard ratios (HRs) and 95% CIs for the association between OCs (time-varying current use and age at first use) and incident fibroids. Fibroid growth was defined as change in log-volume per 18 months for fibroids matched at successive visits. Incidence and growth models were adjusted for time-varying demographic and reproductive factors.
Of 1,232 fibroid-free participants at enrollment, 122 (10%) were current OC users, 79 (6%) first used OCs before age 15 years, and 295 (24%) developed incident fibroids over the study. Current OC use was not associated with risk of incident fibroids compared to no current use (aHR=1.15; 95% CI: 0.79, 1.69), yet was associated with a 13.7% reduction in fibroid growth (95% CI: -24.2%, -1.7%). Risk of incident fibroids was decreased for those who began using OCs before age 15 (aHR=0.53; 95% CI: 0.30, 0.94), but average fibroid growth differed little by age at first use.
Results from this ultrasound-based, prospective fibroid study add important data to understanding the complex relationship between OC use and fibroids.