Objective Assess risk factors for incident and endometrial Mycoplasma genitalium infection and determine if M. genitalium is associated with histological endometritis, an indicator of pelvic inflammatory disease.

Methods This study was a secondary data analysis within the T cell Response Against Chlamydia (TRAC) Study, a prospective evaluation of 246 women with or at risk for Chlamydia trachomatis from urban outpatient clinics, who were followed quarterly for 12 months. Risk factors for incident M. genitalium infection were determined by Cox regression. Relative risks were estimated by Poisson regression with robust error measurements for models examining the association between M. genitalium and endometritis (histological evidence of plasma cells in endometrial stroma and neutrophils in the endometrial epithelium) and for models examining risk factors for detection of endometrial M. genitalium infection.

Results M. genitalium prevalence was 16.7%, incidence was 25.3 per 100 person-years and 23% had repeated positive tests. Black race (non-black HR_adj 0.4, 95% CI 0.2 to 0.9), less education (HR_adj 2.4, 95% CI 1.2 to 5.1) and a new sexual partner (HR_adj 3.1, 95% CI 1.7 to 5.4) were associated with incident M. genitalium. M. genitalium was associated with endometritis (RR_adj 2.0, 95% CI 1.1 to 3.7). Trichomonas vaginalis (RR_adj 2.0, 95% CI 1.2 to 3.4) and endometrial C. trachomatis (RR_adj 1.7, 95% CI 1.1 to 2.8) were associated with endometrial M. genitalium.

Conclusions M. genitalium is prevalent in women at high risk for C. trachomatis, persists over multiple follow-up visits and is associated with histological endometritis. Studies are needed to determine if screening for M. genitalium will improve reproductive outcomes.