Does bacterial vaginosis increase risk of developing uterine fibroids?

“Reproductive tract infections are hypothesized to influence the development of uterine fibroids, yet few studies have investigated the common condition of BV,” wrote the authors of the study funded by the National Institute of Environmental Health Sciences (NIEHS).“Literature is currently limited to data using self-report of BV.”

The study of 200 women (100 cases and 100 controls) was from the Study of Environment, Lifestyle, and Fibroids (SELF): a community-based volunteer sample of 1,693 African-American women, aged 23 to 35, from the Detroit, Michigan, area, who were recruited from 2010 to 2012.

Women were ineligible for SELF if they had a prior clinical diagnosis of UFs; a hysterectomy; ever taken medication to treat lupus, Grave’s disease, Sjogren’s scleroderma or multiple sclerosis; or any type of cancer treated with radiation or chemotherapy.

In total, 1,310 of the women were free of UFs and prospectively followed in the clinic roughly every 20 months over 5 years to identify the incidence of UFs with standardized ultrasound examinations.

The investigators used quantitative polymerase chain reaction (PCR) to assess 9 BV-associated and 4 Lactobacillus species from vaginal swab specimens.

Quantitative PRC (qPCR) results were inconclusive for 3 women, leaving a sample of 197 (99 cases, 98 controls).

Contrary to the authors’ hypothesis, they found no increase in the incidence of UFs or number of UFs among women with more BV-associated bacteria. In fact, a high imbalance of only BV-associated bacteria, without "optimal" Lactobacillus bacteria, was inversely associated with UF incidence: odds ratio (OR): 0.38; 95% confidence interval: 0.17 to 0.81.

Overall, 52% of the cohort had a high imbalance. Those with high imbalance were least likely to have UFs, while those with low imbalance (higher quantities of “optimal” Lactobacillus) were more likely to have UFs.

“This is the first study of ultrasound-detected incident fibroids and molecular vaginal bacterial assessment,” wrote the authors.

When comparing UF cases to controls, proportionately fewer cases had a high body mass index (BMI), heavy alcohol use, smoking history, both chlamydia and herpes seropositivity, higher numbers of sex partners and more likely to have a college degree.

When comparing cases above median total BV-associated bacteria concentrations to those below median total BV-associated bacteria concentrations, those above were younger and proportionately more likely to have high BMI, smoking history, heavy alcohol use, douching history, higher numbers of sex partners, lower age at sexual initiation and both chlamydia and herpes seropositivity. But fewer below median earned a college degree and/or currently used hormonal contraceptives.

In descriptive comparisons, controls had a higher percentage of L. iners (88% vs. 76%) and BV-associated bacteria, except for Prevotella spp., whereas cases had higher percentages of “optimal” Lactobacillus bacteria.

Also, among women with detectable levels of all assessed BV bacteria, Ca. Lachnocurva vaginae, Prevotella spp. and L. gasseri tended to be at higher concentrations in controls, while M. indolicus and L. crispatus tended to be at higher concentrations in cases.

Conversely, the median (25th and 75th percentiles) of the sum of the BV-associated bacteria log10 concentrations was lower in cases: 22 copies/µl vs. 34 copies/µl in controls.

The study’s finding that over half of the women lacked the Lactobacillus species believed to be associated with vaginal health “reinforces the need for more study into what constitutes vaginal health among African Americans, as well as variation in microbiota among other understudied ethnic groups,” the authors concluded.

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Reference

1. Moore KR, Tomar M, Umbach DM, et al. Bacterial vaginosis-associated bacteria and uterine fibroids: a nested case-control study. Sex Transm Dis. Published online May 14, 2021. doi:10.1097/OLQ.0000000000001466