Racial Variation in Vaginal pH Among Healthy Sexually Active Adolescents

BACKGROUND AND OBJECTIVES: To determine if there are racial differences in vaginal pH that could account for the increased prevalence of trichomoniasis among sexually active black women. STUDY DESIGN: We measured the pH of vaginal secretions in a group of 273 sexually active, adolescent females without evidence of lower genital tract infection or cervical inflammation. RESULTS: Univariate analyses revealed that seven factors (black race, current alcohol use, nonsmoking status, gravidity, parity, and younger chronologic and gynecologic age) were significantly associated with a more alkaline vaginal pH. After a step-wise multiple regression analysis only three factors (black race, current alcohol use and parity) remained significantly related to vaginal pH, with the strongest association for black race (mean + standard deviation [SD] for vaginal pH among black adolescents 5.3 + 0.7 compared to 4.7 + 0.6 for other adolescents; P < .0001). CONCLUSION: The pathophysiologic mechanisms that underlie the racial differences we identified in vaginal pH remain to be elucidated. Nevertheless, we speculate that race-related variations in the pH of normal vaginal secretions may decrease the resistance of black adolescents, one of the highest-risk obstetric population in this country, to common vaginal infections, such as trichomoniasis and bacterial vaginosis.