A Better Understanding of Bacterial Vaginosis (BV)

What is Bacterial Vaginosis?

Bacterial Vaginosis (BV) is the most common genital tract disorder in reproductive aged women. It is characterized by a shift from a healthy vaginal microbiome that is dominated by acid-producing bacteria (the healthy bacteria, such as lactobacillus) to a vagina dominated by unhealthy bacteria, including anaerobic bacteria and mycoplasma species.

Will BV Affect My Chances for Getting Pregnant or Having a Healthy Pregnancy?

BV is three times more common to be found in infertile women than fertile women. BV, and other infections in general, can cause decreased fertility in a number of ways:

  • increasing inflammation and immune system activity, making a toxic environment for reproduction.
  • causing damage to sperm and vaginal cells.
  • interfering with the production of healthy cervical mucus during ovulation.
  • blocking the Fallopian Tubes through scar tissue damage from infections, so that sperm and egg can’t meet.

BV is also associated with a two-fold increase in risk of preclinical pregnancy loss, sometimes called a chemical pregnancy, following IVF. BV is also associated with increased rates of human papillomavirus (HPV) and HIV infection. For women with BV present during pregnancy, there may be an increased risk of miscarriages, preterm birth, and low birth weight complications for the newborn, as well as postpartum infections.

How Does BV Develop and What Are Common Treatments?

BV develops because of changes in the pH of the vagina. For women with the most common mix of vaginal bacteria, an acidic vaginal pH is maintained by the production of lactic acid.  This pH of around 4.5 keeps the BV related bacterial types at a low level.  This also causes normal exfoliation, or shedding, of vaginal mucosal cells, which releases glycogen for the good bacteria to eat. And this low pH stimulates white blood cell immunity in the vagina.  BV occurs when the acidic pH of the healthy vagina becomes disrupted.

Antibiotics such as metronidazole, clindamycin, and tinidazole are often prescribed and will destroy some of the bacteria that cause symptoms of bacterial vaginosis. It is a well understood concept that antibiotics kill off not only bad bacteria but good bacteria as well with potentially dire impacts. In a groundbreaking study published in Nature, Martin Blaser of New York University’s Langone Medical Center maintains that antibiotics’ impact on friendly bacteria is permanent.1 Blaser argues that the consequences of this are so serious that antibiotic prescriptions should not be given to pregnant women and young children.

Given that vaginal health correlates to the presence of good bacteria, antibiotics must be used only when necessary. Killing off the good bacteria along with the bad can lead to vaginal imbalance and recurring instances of BV. Studies have shown that more than 50 percent of women treated for BV will experience a recurrence within 12 months.2 BV is most typically recurrent following a course of antibiotics. As with all things involving bacteria in our bodies, the best course of action is to help our bodies heal itself by putting the good bacteria back in charge. If you and your doctor feel a course of antibiotics is necessary, make sure to do extra things such as using probiotics and pH balancing gels to ensure your relief is more than temporary.

Why is Diagnosing BV So Tricky?

One of the frustrating aspects of BV has been an inability to consistently diagnose the disease. Initially, BV was diagnosed using the Amsel Criteria – if a woman had three of the following signs, they would be given a BV diagnosis:

  • a vaginal pH over 4.7
  • a grey vaginal discharge
  • a fishy vaginal odor, that arose after exposure of vaginal secretions to a chemical in the clinic and/or
  • the presence of vaginal epithelial cells coated in bacteria, called “clue cells”

In 1991, this diagnostic method gave way to the Nugent Criteria, which used Gram Staining to look at the bacterial populations in the vagina. Rather than relying on subjective determinations of malodor and/or discharge, a microscope was used to study the bacterial flora. But suddenly, women who had no symptoms of vaginal malodor or disease were being falsely diagnosed with BV! Over time it was determined that these false diagnoses were occurring because several types of healthy lactobacillus bacteria closely resemble the abnormal BV bacteria during staining and microscopic exam. In many clinical practices today, the Amsel Criteria is used in conjunction with Gram Staining to diagnose BV. Nugent Criteria use is limited to facilities with access to a trained microscopist.

While the presence of malodor is an important symptom in the diagnosis of BV, it can inadvertently lead to a false diagnosis. About 50% of women experience unwanted vaginal odor at some point in their lives. Because of the complexity of BV diagnosis, some women who are experiencing feminine odor are misdiagnosed with BV and over-treated with antibiotics.

Complicating things is the recent discovery that baseline bacteria population differ by race. Some women seem to normally have less lactic acid producing bacteria in their vaginal ecosystem, even though they have no symptoms of any disease. The type of vaginal population present in women is called their Community State Types (CSTs). So far, 5 CSTs have been well identified. However, even within your CST, the bacteria in the vagina is always changing. A woman’s period, her ovulation, and her sexual activities can change the types of bacteria in the vagina at a given time. And as a woman ages and her hormone levels change (after about 30 years of age), her vaginal ecosystem also changes. These naturally occurring CSTs and changes in bacteria population make it difficult to predict the effectiveness of broad spectrum antibiotics during a bout with BV.

We now know that the bacteria that causes BV is often present in the vaginas of normal, healthy women in low numbers. It is not yet well understood why these bad bacteria start to take over and displace the “good” lactic acid bacteria, which ultimately leads to BV. BV occurs only when “bad” bacteria species out-compete the healthy lactic acid producing bacteria, and a biofilm or coating of bad bacteria occurs. A single Gram Stain swab of vaginal secretions taken just before the bad bacteria tilts the balance may lead to an inaccurate diagnosis.

How Does BV Impact My Overall Vaginal Health?

BV impacts the vagina’s immune responses. Women with BV have an increase in vaginal chemicals associated with inflammation, called interleukins. The white blood cells that fight infection are also compromised, making them more prone to other vaginal infections. The BV-type bacteria also produce the bad smelling chemicals that women experience as unwanted vaginal odor often described as fishy or ammonia-like.

Antimicrobial peptides (AMPs) that fight invading bacteria are normally made by the vaginal mucosal cells. In women with BV, AMP levels are decreased. Iron, zinc and manganese are required micronutrients for the healthy vaginal ecosystem. Abnormal levels of these nutrients (from dietary causes) may increase BV risk. Women with BV have reduced levels of amylase in the vagina, so that glycogen for lactobacillus to eat becomes limited and the good lactic acid bacteria can’t grow. A helpful diagram and discussion about vaginal ecosystem health can be found here.

For about 90% of women that get BV, it develops following a transient and then persistent loss of lactic acid producing bacteria in the vagina. If conditions that favor lactic acid producing bacteria reoccur, the unhealthy BV state will reverse. However, if the bad bacteria populations continue to grow, there won’t be enough glycogen or manganese to feed the healthy lactobacillus species of bacteria. The BV bacteria then make a biofilm at an elevated pH that coats and protects these bad bacteria, making it difficult for the lactobacillus to return to healthy levels.

Getting the Proper BV Diagnosis and Treatment

Women who test positive for BV type bacteria may have one of three things going on:

  1. a temporary shift in vaginal bacteria populations, such as that seen after menstruation
  2. a permanent but normal healthy CST that includes these bacterial types
  3. a long lasting change from her previously healthy lactic acid producing CST that results in actual BV and requires treatment

Determining which category a woman falls into is critical so as to not over-treat and actually cause vaginal disease!

Diagnosing and treating BV requires engagement with a healthcare provider who is aware of the latest developments in the field. New studies suggest that some antibiotics (e.g. erythromycin) selectively kill lactobacillus, whereas others like tetracycline do not. Other options to try may include: oral supplementation with healthy doses of micronutrients (such as iron, zinc and manganese), and use of vaginal gels that help maintain the physiologic vaginal pH at ~4.5.

In choosing a product to help eliminate odor and maintain pH, choose products with NO glycerin, oils or parabens. It is also important to select a product that is isotonic with vaginal cells, meaning that the salt/ion concentration of the product is the same as your vaginal tissues. Many freshening gels have salt (ion) concentrations that are 4 times higher than vaginal fluids. High salt levels have been found to damage vaginal mucosal cells and lactobacillus. Comparing the choices for vaginal freshening gels is simplified for you here.

A critical take away on the newest science about BV is that occasional unwanted vaginal odor occurs in about 50% of women. And, although vaginal odor is found in women with BV, just because you experience odor does not mean that you have BV. Temporary unwanted vaginal odors can occur for a variety of reasons. If you experience unwanted odor, try a freshening gel like IsoFresh to eliminate odor in an isotonic gel biomatched to healthy vaginal pH. Always remember that BV can have serious health consequences. If you have chronic discharge or ongoing foul odor, talk to a health care provider.

Adapted from Nasioudis et al. Bacterial Vaginosis: A critical analysis of current knowledge. BJOG 2017;124:61-69

1Blaser MJ. Stop the killing of beneficial bacteria. Nature 476, 393–394 (25 August 2011). doi:10.1038/476393a
2Bradshaw CS, et al. (2006). “High recurrence rates of bacterial vaginosis over the course of 12 months after oral metronidazole therapy and factors associated with recurrence” J Infect Dis. 2006 Jun 1;193(11):1478-86.