Bacterial Vaginosis


Bacterial vaginosis (BV) is the most common of three vaginal infections that fall under the category known as vaginitis. The other two infections are trichomoniasis, a sexually transmitted disease, and the fungal infection commonly known as a yeast infection.

BV is the least understood and most often ignored or misdiagnosed of these conditions. However, it is gaining more attention as more research shows that untreated BV can lead to significant health complications, including premature delivery, postpartum infections, clinically apparent and subclinical pelvic inflammatory disease (PID), postsurgical complications (after abortion, hysterectomy, cesarean section and other reproductive procedures), increased vulnerability to HIV infection and, possibly, infertility. As many as one-third of women in the United States have BV.

BV is now considered a sexually transmitted disease. Women who have a new sex partner or multiple sex partners are at an increased risk for getting BV, although it is occasionally diagnosed in women who have never had sex. Douching also appears to increase the risk of developing BV.

BV has gone by different names in the past, including nonspecific vaginitis and Gardnerella vaginalis vaginitis. BV is simpler to remember, but there is nothing simple about this condition, and it is not harmless, as was once believed.

BV is actually a syndrome resulting from an imbalance in the different types of bacteria in the vagina (also called vaginal “flora”). A healthy vagina has numerous organisms that naturally live there. The vast majority—about 95 percent—belong to a type of bacteria called lactobacillus.

There are several kinds of lactobacillus, at least one of which is responsible for keeping the vagina’s pH at normal levels. One hypothesis claims that when these levels become unbalanced, certain microorganisms may overtake the normal flora leading to a low-grade infection that often produces an abnormal vaginal discharge.


With many negative outcomes now linked to bacterial vaginosis (BV), it is important that women get tested and treated. But surveys find that the majority of health care professionals don’t routinely test for or treat BV. And yet an estimated 29 percent of women aged 14 to 49 and 50 percent of African American women have BV.

The most common symptoms include a discharge and an unpleasant vaginal odor. Women may easily mistake BV for a yeast infection, which is caused by the overgrowth of fungi called Candida albicans. However, BV requires a different treatment, so it is important you get an accurate diagnosis. Additionally, you may have more than one type of vaginitis at the same time, so having a yeast infection doesn’t mean you can’t also have BV.

Fortunately, a trained health care professional can easily diagnose BV. All it takes is a test to check the level of acidity, or pH, in the vagina. A vaginal pH greater than 4.5 is one sign you may have BV.

Your health care professional will also take a vaginal discharge specimen for examination under a microscope to look for “clue cells”—cells from the vaginal lining that are covered with bacteria. It is important not to douche or use deodorant sprays before a medical exam because these products can make it more difficult to diagnose BV.

In addition to measuring the vaginal pH and checking for clue cells, your health care professional may place a drop of 10 percent potassium hydroxide on a vaginal fluid specimen and check the odor. Several commercial tests also are available to diagnose BV. Cultures for Gardnerella vaginalis alone and cervical Pap tests are not accurate methods for diagnosing BV.

The most common symptom of BV is a vaginal discharge similar in consistency and appearance to skim milk. The discharge caused by the infection often has a strong “fishy” odor that may become worse after sex because semen changes the acidic level of vaginal fluids. BV also may cause vaginal itching and irritation. About 50 percent to 75 percent of all women with BV experience no symptoms.


As with other vaginal infections, the primary goal in treating bacterial vaginosis (BV) is to relieve signs and symptoms of infection. All women with symptoms should be treated.

BV is treated with antibiotics. The most common therapies are metronidazole (Flagyl), and clindamycin (Cleocin). Both metronidazole and clindamycin are available by prescription in oral (pill) form, and metronidazole is available in a gel (MetroGel-Vaginal), and clindamycin is available in a cream (such as Clindesse) that you insert into the vagina. Generic versions of these antibiotics also are available and effective.

If your symptoms disappear with treatment, you don’t have to see your health care professional again. One round of treatment usually works in about 70 percent of cases. However, BV frequently recurs and can be chronic in some women.

Don’t drink any alcohol while using metronidazole (either oral or vaginal) because it may make you nauseous and/or lead to severe vomiting. Also, if you’re using intravaginal forms of clindamycin, the oil-based medication may weaken latex condoms or diaphragms. Topical clindamycin may rarely cause colitis, a potentially life-threatening infection of the colon.

Talk to your health care professional about this risk and be sure to alert him or her if you experience severe diarrhea, stomach cramping or blood in your stool while taking clindamycin or within a few weeks of stopping it. Over-the-counter treatments available for some vaginal infections (Candidiasis, or “yeast” infections) are NOT effective for BV.

While you’re being treated for BV, you may be advised not to have sex; if you do have sex, your partner should wear condoms. Treating your male partner isn’t necessary, however, since studies find it doesn’t help prevent another infection. Female partners may need treatment, however.

Treatment is more complicated for pregnant women. If you’ve previously delivered a premature infant, you may be tested for BV during your first prenatal visit. If you have the infection, you should be treated promptly.

Regardless of other risk factors for preterm delivery, all symptomatic pregnant women should be tested and treated. However, most studies show no difference in risk of preterm delivery in asymptomatic women who don’t get treated versus those who get treated. Thus, pregnant women with asymptomatic BV don’t require treatment.

In any case, pregnant women who are going to be screened should have this done during the first prenatal visit.


Numerous factors may be associated with vaginal infections. Although no single factor has emerged as a primary cause, experts say healthy diets and behavior are the best medicine.

One of the more disturbing aspects of bacterial vaginosis (BV) is that the infection frequently returns after treatment. About 30 percent of women have a recurrence within three months of treatment. While the reasons for recurrent BV are not well understood, long-term maintenance treatment may be recommended for women with frequent recurrences of BV.

However, you should take all prescribed medicines as recommended to decrease the likelihood of recurrence. Continue taking the medicine as you’ve been directed even if your symptoms disappear.

One cause of recurrent BV may be that even after the harmful bacteria that replaced the “good” bacteria is gone, the “good” bacteria have trouble growing back in the vagina.

Most women with recurrent BV infection respond well to therapies that help maintain the ratio of “good” to “bad” bacteria in the vagina. One such therapy is metronidazole gel (0.75 percent) for seven to 10 days followed by an application twice a week for four to six months.

Here are some tips that may decrease the risk of BV or recurrent BV:

  • Don’t douche. Douching upsets the normal pH balance of the vagina.
  • Avoid sexual contact with someone who has a sexually transmitted disease; use condoms if you’re uncertain.
  • Avoid local irritants such as bubble baths, harsh soaps, feminine hygiene sprays and deodorant tampons, all of which can affect the normal pH of the vagina.
  • Reduce semen exposure (which can affect the vaginal bacteria balance) by using condoms.
  • Don’t smoke.
  • If you develop BV three or more times in a year, talk to your health care professional about alternating medications or using intravaginal metronidazole as a prophylactic for three to six months.
  • Facts to Know

    1. Half of all African-American women aged 14 to 49 in the United States have BV. This may help explain why African-American women have higher rates of problem pregnancies. The reason for increased BV in this population is not clear.

    2. BV is widespread but its prevalence varies widely. BV is the most common cause of vaginitis in women of childbearing age—almost one in three women in the United States has BV.

    3. BV increases a woman’s risk of delivering prematurely or delivering a baby with low birthweight. A National Institutes of Health study found that pregnant women with BV were more likely to deliver a baby with low birthweight than those without the infection. The most common cause of premature birth from BV is premature rupture of membranes.

    4. A woman with BV may be more likely to become infected with HIV, the sexually transmitted virus that causes AIDS (acquired immunodeficiency syndrome). Recent studies have shown a relationship between BV and HIV, so health officials now consider BV a risk factor for HIV acquisition, particularly in developing countries where BV is often untreated.

    5. Bacterial vaginosis infection disrupts the vaginal ecosystem. Some women infected with BV may have up to 1,000 times more anaerobic bacteria (bacteria that require no oxygen to live) than uninfected women. Once this imbalance occurs, the body has difficulty getting back to normal. Consequently, researchers are looking at natural ways to supplement the “good” bacteria needed to protect the genital tract from infection, and thereby reduce recurrences.

    6. Because its symptoms mimic other vaginal infections, BV is often mistaken for a common yeast infection.

    7. About 50 percent to 75 percent of women with BV have no symptoms. And yet studies find that as many as one-third of women entering obstetric clinics have a BV infection.

    8. Despite adequate treatment, BV recurs in 30 percent of women within three months. Researchers are not sure what makes some women more prone to recurrent BV.

    9. The greatest risk factors for BV are having a new sex partner or having multiple sex partners.

    10. Probiotics currently available are not effective in preventing or curing BV.