If you’ve been diagnosed with bacterial vaginosis (BV), you’ve probably heard that it isn’t a sexually transmitted infection or disease… but sex can still worsen symptoms. How can that be? Let’s explore why that distinction isn’t splitting hairs, what causes BV in the first place, its connection with some forms of contraceptive use, and why treatment is only temporary.
What bacterial vaginosis (BV) is
Bacterial vaginosis is a disruption and imbalance in the vaginal microbiome (we’ve talked about the gut microbiome before, здесь, including how Dad’s микробиом кишечника affects his baby in utero, and about how Mom’s vaginal microbiome seeds baby’s gut microbiome) [1]. The vaginal microbiome содержит billions, yes, billions, of microbes (microscopic organisms) [1]. The most common types of microbes include bacteria, viruses, and fungi.
We know that some microbes are healthy for the body (in other words, not all bacteria is bad!), and that баланс is important: certain bacteria should exist in certain amounts in relation to other types of bacteria. Lactobacillus is a “good” type of bacteria, and while the bacterial composition of the microbiome changes over the course of the menstrual cycle as well as during a woman’s reproductive lifespan overall, in a healthy vagina, лактобактерии should be the dominant bacteria throughout. Lactobacilli help protect the vagina from infection.
But when a woman has BV, she has an overgrowth of a different type of bacteria—anaerobic bacteria, especially Gardenerella vaginalis. Fascinatingly, in BV, anaerobic bacteria increase by 100-1000x the normal amount. These excessively high bacterial counts, specifically of anaerobic bacteria, lead to the development of biofilms (think of a shield or matrix) on the skin cells of the vagina. These biofilms are notoriously resistant to antibiotics. This makes a woman more vulnerable to developing infections, and the biofilms make BV hard to permanently treat.
In BV, anaerobic bacteria increase by 100-1000x the normal amount. These excessively high bacterial counts lead to the development of biofilms on the skin cells of the vagina. These biofilms are notoriously resistant to antibiotics. This makes a woman more vulnerable to developing infections, and the biofilms make BV hard to permanently treat.
Who gets BV, and why?
The short ответ is: many women. An estimated 23-29% of reproductive-aged women globally have BV [2]. For reference, an estimated 5-10% of women worldwide experience эндометриоз [3]. In North America, African American and Hispanic women are more likely than white and Asian women to have BV.
Disconcertingly, 60 years of research haven’t yielded clear answers on what causes the explosion of “bad” bacteria and/or the decrease of “good” bacteria that characterizes BV. We do know that IUD use, especially copper IUD use, appears to raise риск [2]. Male promiscuity is also associated with increased risk of BV for female partners [2]. Women who have sex with other women are also at high risk, probably because of the exchange of vaginal fluids.
Having BV increases your risk of certain reproductive conditions
While BV is not a sexually transmitted infection or disease, it does increase your risk of contracting sexually transmitted infections, such as chlamydia and gonorrhea, as well as human papilloma virus (HPV) and human immunodeficiency virus (HIV) [1].
BV also makes women more susceptible to reproductive system infections, especially pelvic inflammatory disease (PID), cervical infections, and endometrial infections, plus urinary tract infections (UTIs) [4].
BV is linked with miscarriage and preterm birth [1]. Being born early is associated with having a low birth weight, which in turn comes with short-term and long-term risks for the baby [4].
BV symptoms
A 2022 review article in Clinical Infectious Diseases called BV “the most common cause of vaginal discharge” [2]. Unlike the egg-white cervical mucus that signals health and fertility, the discharge associated with BV is often green, gray or milky-looking and/or has a distinct fishy or metallic odor. BV commonly causes itching, which may be worse, along with the smell, after sex or during menstruation. This is because sperm and menstruation both temporarily change the vaginal pH. Still, BV is не considered a sexually transmitted infection, because many women who are not sexually active (including those who have never had sex) have BV.
BV is diagnosed based on multiple criteria, including results from a vaginal swab that can be performed during a routine visit to your primary care practitioner or OB/GYN’s office. Interestingly, more than half of women with BV have no symptoms [4].
BV is tough to treat and comes back quickly
Remember the biofilm mentioned above? That biofilm shields or protects the out-of-control anaerobic bacteria from “crowd control” by antibiotics. Worse, antibiotics can’t restore healthy Lactobacillus. For these reasons, BV is notoriously difficult to treat and comes back quickly, often by just six months later.
Even though BV is tricky to treat, women with symptoms still receive round after round of antibiotics anyway in an effort to avoid the other infections listed above or, for pregnant women, the possibility of preterm birth. Treatment for pregnant women is especially precarious because antibiotics impact the woman’s gut microbiome, and her gut microbiome indirectly affects her baby’s brain development [4] [5]. Some research suggests that vaginal antibiotics are safer than oral antibiotics for the baby [4]. Antibiotic resistance is a possibility with repeated antibiotic rounds over time, in both pregnant and nonpregnant women.
Can probiotics help?
Above, you read that BV keeps coming back in part because antibiotics can’t restore normal levels of лактобактерии. You might know that лактобактерии is a commonly sold probiotic, and you may wonder why women can’t just take a probiotic with (or instead of) conventional antibiotics?
Unfortunately, research on oral probiotics hasn’t yet shown clear benefit (for interested readers, details are здесь и здесь) [4] [6]. As with oral probiotics, vaginal probiotics are difficult to compare because the strains of probiotics used often vary from one study to the next. Still, probiotics may represent the most benefit for BV treatment, once dosages and strains can be figured out [7]. One particular strain, lactobacillus rhamnosus BMX 54, has some promising research backing it, especially when combined with a simple sugar prebiotic [7] [4].
Unfortunately, research on oral probiotics hasn’t yet shown clear benefit. As with oral probiotics, vaginal probiotics are difficult to compare because the strains of probiotics used often vary from one study to the next. Still, probiotics may represent the most benefit for BV treatment, once dosages and strains can be figured out.
Other potential BV treatments of the future include vaginal microbiome transplantation (transferring good bacteria from one healthy volunteer to an infected woman), medications that directly attack the biofilm, and certain viruses (bacteriophages) that reduce bacterial overgrowth while preserving healthy bacteria [4]. Some practitioners may also recommend vaginal boric acid as an adjuvant therapy alongside antibiotics, but it is toxic when taken orally, and should not be taken while pregnant.
Итоги
While many women don’t know they have bacterial vaginosis because they don’t have symptoms, it nevertheless represents a health concern because it predisposes women to other infections and pregnancy complications. Currently, treatment options are very limited and recurrence is common. The best advice we have for evidence-based options is: stay tuned. We hope there will be better options yet to come.
Ссылки
[1] Chen, Xiaodi & Lu, Yune & Chen, Tao & Li, Rongguo. (2021). The Female Vaginal Microbiome in Health and Bacterial Vaginosis. Frontiers in Cellular and Infection Microbiology. 11. 10.3389/fcimb.2021.631972.
[2] Christina A Muzny, Jennifer Balkus, Caroline Mitchell, Jack D Sobel, Kimberly Workowski, Jeanne Marrazzo, Jane R Schwebke, Diagnosis and Management of Bacterial Vaginosis: Summary of Evidence Reviewed for the 2021 Centers for Disease Control and Prevention Sexually Transmitted Infections Treatment Guidelines, Clinical Infectious Diseases, Volume 74, Issue Supplement_2, 15 April 2022, Pages S144–S151, https://doi.org/10.1093/cid/ciac021
[3] Dong Yi Shen, Jing Li, PanWei Hu, Cong Qi, Hong Yang, Global, regional, and national prevalence and disability-adjusted life-years for endometriosis in 204 countries and territories, 1990–2019: Findings from a global burden of disease study, European Journal of Obstetrics & Gynecology and Reproductive Biology: X, Volume 25, 2025, 100363, ISSN 2590-1613, https://doi.org/10.1016/j.eurox.2024.100363.
[4] Eleni Dubé-Zinatelli, Luna Cappelletti, Nafissa Ismail, The vaginal microbiome in bacterial vaginosis: Pathogenesis, reproductive impacts, and emerging therapies, Journal of Reproductive Immunology, Volume 172, 2025, 104804, ISSN 0165-0378, https://doi.org/10.1016/j.jri.2025.104804.
[5] Eman A. Mady, Ahmed S. Doghish, Walaa A. El-Dakroury, Samy Y. Elkhawaga, Ahmed Ismail, Hesham A. El-Mahdy, Elsayed G.E. Elsakka, Hussein M. El-Husseiny,Impact of the mother’s gut microbiota on infant microbiome and brain development,Neuroscience & Biobehavioral Reviews, Volume 150, 2023, 105195, ISSN 0149-7634, https://doi.org/10.1016/j.neubiorev.2023.105195.
[6] Baldacci, F., Baldacci, M., & Bertini, M. (2020). Lactobacillus rhamnosus BMX 54 + Lactose, A Symbiotic Long-Lasting Vaginal Approach to Improve Women’s Health. International Journal of Women’s Health, 12, 1099–1104. https://doi.org/10.2147/IJWH.S259311
[7] Chen, R., Li, R., Qing, W. и др. Probiotics are a good choice for the treatment of bacterial vaginosis: a meta-analysis of randomized controlled trial. Reprod Health 19, 137 (2022). https://doi.org/10.1186/s12978-022-01449-z
