What is bv caused by

The Bacterial Imbalance

Bacterial vaginosis develops when the delicate balance of bacteria in the vagina is disrupted. The vagina normally contains numerous bacterial species, with lactobacilli maintaining an acidic environment that prevents harmful bacteria from proliferating. When this protective population declines, pathogenic bacteria multiply unchecked, creating the characteristic symptoms and complications of BV.

Key Causative Organisms

While Gardnerella vaginalis is often the primary culprit, BV typically involves multiple anaerobic bacteria including Prevotella, Mobiluncus, and Atopobium species. These organisms thrive in oxygen-poor environments and produce volatile fatty acids causing vaginal symptoms. The polymicrobial nature of BV means multiple bacteria species work together rather than a single pathogen being responsible.

Risk Factors and Triggering Events

Several behaviors increase BV risk significantly. Douching disrupts natural vaginal flora and alters pH balance. Multiple sexual partners increase exposure to different bacteria. Intrauterine devices (IUDs) and certain contraceptive methods may increase susceptibility. Antibiotics for other infections eliminate beneficial lactobacilli. New sexual relationships and unprotected intercourse show higher BV incidence. Hormonal changes during menstruation, pregnancy, or menopause also affect vaginal bacteria balance.

pH and Vaginal Environment Changes

Normal vaginal pH is 3.8-4.5, maintained by lactobacillus-produced lactic acid. When this protective acidic environment is lost and pH rises to 4.5-6, anaerobic bacteria flourish. This pH shift is both cause and consequence of bacterial imbalance—harmful bacteria alter the environment while benefiting from it. Understanding pH changes is crucial for recognizing BV development and prevention strategies.

Secondary Triggers

Beyond primary causes, several secondary factors can trigger BV in susceptible individuals. Sexual activity, particularly with new partners, introduces new bacteria. Menstruation brings pH changes. Stress and immune suppression reduce the body's ability to maintain bacterial balance. Smoking may increase BV risk by affecting immune function. Certain personal care products and douching habits also disrupt protective bacterial flora.