ABSTRACTThe most common cause of vaginal discharge is bacterial vaginosis (BV). BV, a dysbiosis of the vaginal microbiome, is inhibited by lactic acid, and lactic acid production is supported by estrogen. Use of estrogen-containing combined oral contraception (COC) has been associated with decreased BV prevalence across several studies. However, most studies relied on self-report to ascertain COC use. We conducted a cross-sectional study of COC use and BV using data from the National Health and Nutrition Examination Survey (NHANES) 2001-2004 cycles; data on COC use was collected from two sources. During the household interview, participants were asked about prescription medication use in the past month. During the NHANES exam, in a private interview, participants were asked about the current use of birth control pills. Vaginal fluid was collected, Gram stained, and scored using the Nugent criteria for BV (scores of 0-3, 4-6, and 7-10 corresponded to negative, intermediate, and positive BV). Among non-pregnant, premenopausal individuals ages 20-49 (unweighted n=1460), we conducted multinomial logistic regression to estimate the adjusted odds ratios (aOR) and 95% confidence intervals (CI), accounting for the complex survey sampling design. The weighted prevalence of prescription medication-derived current COC use was 7%. Current COC use was associated with 67% lower odds of intermediate Nugent-score BV (aOR 0.33; 95%CI 0.18-0.63) and 83% lower odds of positive Nugent-score BV (aOR 0.17; 95%CI 0.07-0.42) compared to non-use. In contrast, the weighted prevalence of self-reported current OC use was 18%. For self-reported current OC use, we observed lower odds of intermediate Nugent-score BV (aOR 0.50, 95%CI 0.34-0.75) and positive Nugent-score BV (aOR 0.48; 95%CI 0.30-0.79). COC use based on prescription information yielded a stronger association than that based on self-report. Further research investigating the pharmaceutical aspects of COC use on BV prevalence is warranted.
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