Untreated bacterial vaginosis can progress from a manageable imbalance to a source of serious complications, including chronic recurrence, increased vulnerability to sexually transmitted infections, pregnancy risks, and surgical complications. Many people with BV have mild or no symptoms at first, which makes it easy to ignore. But the longer BV persists, the harder it becomes to resolve, and the more damage it can do to the vaginal environment and reproductive health.
BV Becomes Harder to Treat Over Time
The bacteria behind BV, primarily species of Gardnerella, don’t just float around in the vaginal canal. They attach to the vaginal lining and build protective structures called biofilms. These biofilms act like a shield, making it harder for your immune system and even antibiotics to reach the bacteria inside. Gardnerella species also produce enzymes that break down vaginal mucus and can even degrade immune molecules your body sends to fight them off. This is essentially an immune evasion strategy that lets the infection dig in deeper the longer it’s left alone.
This persistence is a major reason BV is so notoriously difficult to cure once it’s established. Between 50% and 80% of women who are treated for BV will experience a recurrence within 6 to 12 months. Research shows that even after antibiotic treatment, Gardnerella and other BV-associated bacteria remain enriched in the vaginal microbiome, suggesting that microbial persistence, not reinfection from an outside source, drives most recurrences. The longer BV goes untreated, the more entrenched these biofilms become, and the more likely you are to end up in a frustrating cycle of repeated infections.
Your Vaginal Microbiome Shifts in a Damaging Way
A healthy vagina is dominated by Lactobacillus bacteria, which produce lactic acid and keep the environment acidic (typically below a pH of 4.5). This acidity is protective. It suppresses the growth of harmful organisms and acts as a frontline defense against infections. When BV takes hold, Lactobacillus populations collapse and are replaced by a diverse mix of anaerobic bacteria. Vaginal pH rises above 4.5, creating an environment where harmful microbes thrive.
Left untreated, this shift tends to stabilize in the wrong direction. The Lactobacillus-depleted state becomes self-reinforcing: without enough acid-producing bacteria, the conditions that favor BV-causing organisms persist, and Lactobacillus has a harder time reestablishing itself. This isn’t just an abstract microbiological problem. The loss of that protective acidic barrier leaves you more vulnerable to other infections, including STIs like chlamydia, gonorrhea, herpes, and HIV.
Pregnancy Complications
Untreated BV during pregnancy carries real risks for both the mother and baby. BV is associated with roughly a 2- to 3-fold increased risk of preterm delivery. It’s also linked to premature rupture of membranes (when the water breaks too early), intra-amniotic infection, and postpartum endometritis, an infection of the uterine lining after delivery.
The CDC recommends treatment for all symptomatic pregnant women with BV because of these associations. For asymptomatic pregnant women, the picture is more nuanced. Routine screening isn’t currently recommended for all pregnancies, but for women with a history of preterm birth or late miscarriage, the evidence leans toward treatment being beneficial. Four out of seven clinical trials in that high-risk group showed improved outcomes with treatment, though results have been mixed overall.
Increased Surgical Infection Risk
If you need a gynecological procedure while you have untreated BV, your risk of developing a postoperative infection goes up. This applies to hysterectomies, surgical abortions, and potentially cesarean deliveries. The disrupted vaginal flora essentially introduces a higher bacterial load into a surgical environment, raising the chance of complications at the surgical site.
Treating BV with appropriate antibiotics before these procedures has been shown to reduce postoperative infection rates. This is why many gynecologists recommend screening for BV before planned surgeries. If you have an upcoming procedure and suspect you might have BV, it’s worth getting tested beforehand rather than assuming it will resolve on its own.
Effects on Fertility
Untreated BV can interfere with conception, both naturally and through assisted reproduction. The chronic inflammation and altered vaginal environment associated with BV are linked to pelvic inflammatory disease and endometritis, both of which can damage the reproductive tract and contribute to infertility over time.
For women undergoing IVF, the composition of the vaginal microbiome appears to matter for success. Women with low levels of Lactobacillus in their vaginal samples at the time of embryo transfer were significantly less likely to achieve successful implantation. An unfavorable microbiome profile showed a statistically meaningful increase in the risk of failing to become pregnant. Fertility clinics typically treat symptomatic BV before embryo transfer for this reason, but women who don’t realize they have BV may be unknowingly reducing their chances.
Can BV Resolve on Its Own?
Sometimes, yes. Mild cases of BV occasionally clear without intervention as the vaginal microbiome rebalances itself. But “sometimes resolves” is different from “likely resolves,” and there’s no reliable way to predict whose infection will clear spontaneously and whose will persist or worsen. The CDC recommends treatment for anyone with symptoms, and the longer symptoms persist, the less likely spontaneous resolution becomes. The biofilm formation that occurs during untreated BV is a one-way ratchet: each week the infection persists, the protective bacterial structures become more established and more resistant to both your immune system and future treatment.
The characteristic signs to watch for are a thin, grayish-white discharge, a fishy odor (especially after sex), and vaginal irritation. Some people have BV with no noticeable symptoms at all. If you’ve noticed any of these signs and have been putting off treatment, the practical takeaway is straightforward: BV is easier to treat early than late, and the complications of leaving it alone are more serious than most people expect.