Bacterial Vaginosis

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Bacterial vaginosis is the most common type of vaginal infection. To learn more about other common types, see the topics Vaginal Yeast Infections and Trichomoniasis.

What is bacterial vaginosis?

Bacterial vaginosis is a mild infection of the vagina caused by bacteria. Normally, there are a lot of “good” bacteria and some “bad” bacteria in the vagina. The good types help control the growth of the bad types. In women with bacterial vaginosis, the balance is upset. There are not enough good bacteria and too many bad bacteria.

Bacterial vaginosis is usually a mild problem that goes away on its own in a few days. But it can lead to more serious problems, so it’s a good idea to see your doctor and get treatment.

What causes bacterial vaginosis?

Experts are not sure what causes the bacteria in the vagina to get out of balance. But certain things make it more likely to happen. Your risk of getting bacterial vaginosis is higher if you:

• Have more than one sex partner.
• Have a female sex partner.
• Have a sexually transmitted disease (STD).
• Use an IUD for birth control.
• Douche.

You may be able to avoid bacterial vaginosis if you limit your number of sex partners and don't douche.

Bacterial vaginosis is more common in women who are sexually active, but it is not something you catch from another person.

What are the symptoms?

The most common symptom is a smelly vaginal discharge. It may look grayish white or yellow. A sure sign of bacterial vaginosis is a "fishy" smell, which may be worse after sex. About half of women who have bacterial vaginosis do not notice any symptoms.

Many things can cause abnormal vaginal discharge, including some sexually transmitted diseases (STDs). See your doctor so you can be tested and get the right treatment.

How is bacterial vaginosis diagnosed?

Doctors diagnose bacterial vaginosis by asking about the symptoms, doing a pelvic exam, and taking a sample of the vaginal discharge. The sample can be tested to find out if you have bacterial vaginosis.

What problems can bacterial vaginosis cause?

Bacterial vaginosis usually does not cause other health problems. But it can lead to serious problems in some cases.

• If you have it when you are pregnant, it increases the risk of miscarriage, early (preterm) delivery, and uterine infection after pregnancy.
• If you have it when you have a pelvic procedure such as a C-section, abortion, or hysterectomy, you are more likely to get a pelvic infection.
• If you have it and you are exposed to a sexually transmitted disease (including HIV), you are more likely to catch the disease.

Getting treated with antibiotics can help prevent these problems.

How is it treated?

Doctors usually prescribe an antibiotic to treat bacterial vaginosis. The ones used most often are metronidazole and clindamycin. They come as pills you swallow or as a cream or capsules (called ovules) you put in your vagina. If you are pregnant, you will need to take pills.

Bacterial vaginosis usually clears up in 2 or 3 days with antibiotics, but treatment goes on for 7 days. Do not stop using your medicine just because your symptoms are better. It is important to take the full course of antibiotics.

If you are treated with antibiotics:

• Avoid all alcohol use if you are taking metronidazole. This includes over-the-counter medicines that contain alcohol, such as NyQuil. Mixing alcohol and metronidazole can cause severe nausea and vomiting.
• Don't trust condoms or diaphragms if you use antibiotic creams or ovules. These treatments have an oil that can weaken latex. This can cause condoms and diaphragms to fail.

Antibiotics usually work well and have few side effects. But taking them can lead to a vaginal yeast infection. A yeast infection can cause itching, redness, and a lumpy, white discharge. If you have these symptoms, talk to your doctor about what to do.

Frequently Asked Questions

Bacterial vaginosis is caused by an imbalance of the organisms (flora) that naturally exist in the vagina. Normally, about 95% of vaginal flora are lactobacillus bacteria. (These types are unique to humans, different from the lactobacillus in yogurt.) These lactobacilli help keep the vaginal pH level low and prevent overgrowth of other types of organisms. Women with bacterial vaginosis have fewer lactobacillus organisms than normal and more of other types of bacteria. Experts do not yet understand what causes this imbalance.¹

Although the specific cause isn't known, a number of health and lifestyle factors have been linked to bacterial vaginosis. For more information, see the What Increases Your Risk section of this topic.

About half of women with bacterial vaginosis have no telltale symptoms.² Bacterial vaginosis does not typically cause itching. It does, however, cause:

• An excessive grayish white vaginal discharge, unlike normal vaginal discharge (1 in 3 women with bacterial vaginosis describe the discharge as yellow).³
• A bothersome "fishy" odor, which is usually worse after intercourse.

Other conditions with similar symptoms include some sexually transmitted diseases (especially trichomoniasis), urinary tract infection, and vaginal yeast infection.

Bacterial vaginosis often clears up on its own. But in some women it persists, and for many women it comes back after it has cleared up. Antibiotic treatment works for some women but not others.

• About 1 out of 4 women find that bacterial vaginosis clears up without medication after a week.¹
• Bacterial vaginosis recurs in about 1 out of 3 treated women.²

Complications

Your risk of complications from bacterial vaginosis is higher:

• During pregnancy. Compared to pregnant women who don't have it, women who have bacterial vaginosis during pregnancy have higher risks of miscarriage, early (preterm) delivery, and uterine infection after pregnancy.⁴
• After gynecological surgery. Women with bacterial vaginosis at the time of an invasive vaginal procedure have an increased risk of developing more serious infection or inflammation, such as pelvic inflammatory disease (PID), endometritis, or urinary tract infection. Surgical procedures linked to bacterial vaginosis-related infection include endometrial biopsy, surgical abortion, hysterectomy, intrauterine device (IUD) placement, cesarean section, dilation and curettage (D&C), and an X-ray test that examines the inside of the uterus, the fallopian tubes, and surrounding area (hysterosalpingography).⁵
• When exposed to HIV or other sexually transmitted diseases. Women who have bacterial vaginosis when they are exposed to sexually transmitted diseases (including HIV) have an increased risk of becoming infected with the sexually transmitted disease.¹

Factors that increase your risk of developing bacterial vaginosis include:

• Starting sexual activity at a young age.
• An infection (or a recent infection) with certain sexually transmitted diseases (STDs).
• Having multiple sex partners.
• Having a female sex partner.⁶
• Using an intrauterine device (IUD).
• Douching.

Although bacterial vaginosis can be triggered by or get worse from sexual activity, it does not appear to be an infection that is passed from man to woman. Therefore, experts do not consider bacterial vaginosis to be a male-female sexually transmitted disease. It is possible but not proven that bacterial vaginosis is passed from woman to woman during sexual contact.

Bacterial vaginosis can be difficult to distinguish from other types of vaginal infection. Consider the following if you have any signs of vaginal infection.

Call your health professional immediately if you:

• Develop lower abdominal pain and a fever higher than 101°F (38.33°C) along with a vaginal discharge.
• Are pregnant and have symptoms of a vaginal infection.

Call your health professional for an appointment within 1 week if you:

• Develop an unusual vaginal discharge that has a foul odor, especially noticeable after sex.
• Have unusual vaginal itching.
• Have pain during sex or urination.
• Develop any other discomfort or discharge that may indicate a vaginal infection.

If you have not been diagnosed with bacterial vaginosis but have symptoms that cause you concern, see the following topics:

• Vaginal Problems
• Abdominal Pain, Age 12 and Older
• Abnormal Vaginal Bleeding

Watchful Waiting

It's generally recommended that you contact or see your health professional about vaginal symptoms. The only exception to this rule is when you are sure that your vaginal symptoms indicate a vaginal yeast infection. If you have had a yeast infection before and are sure that your problem is a yeast infection rather than bacterial vaginosis, you can consider home treatment with a nonprescription product to treat yeast infections. For more information, see the topic Vaginal Yeast Infections.

If your symptoms are due to a sexually transmitted disease (STD) and not bacterial vaginosis, you may infect a sex partner if you delay treatment. You may also develop more serious complications of STDs such as pelvic inflammatory disease (PID).

• Avoid sex while waiting to see your health professional. This will prevent the spread of a possible infection.
• Avoid douching.

Who To See

Health professionals who can diagnose and treat bacterial vaginosis include:

• Family medicine doctors.
• Gynecologists.
• Nurse practitioners.
• Internists.
• Physician assistants.

To prepare for your appointment, see the topic Making the Most of Your Appointment

Your health professional may only test you for bacterial vaginosis if you:

• Have symptoms.
• Are going to have a hysterectomy or surgical abortion (bacterial vaginosis increases infection risk afterwards).
• Are pregnant and have had a preterm delivery in the past (a past preterm delivery may have been caused by infection).

Your health professional can diagnose bacterial vaginosis based on your history of symptoms, a vaginal examination, and a sample of the vaginal discharge. Laboratory tests to detect signs of bacterial vaginosis may include:

• Wet mount. A sample of vaginal discharge is mixed with a salt (normal saline) solution after placing it on a microscope slide. The prepared slide is examined to identify the bacteria present, to look for white blood cells that indicate an infection, and to look for unusual cells called clue cells. The presence of clue cells is the most reliable indicator of bacterial vaginosis.
• Whiff test. Several drops of a potassium hydroxide (KOH) solution are added to a sample of vaginal discharge to determine whether a strong fishy odor is produced. A fishy odor on the whiff test suggests bacterial vaginosis.
• Vaginal pH. The normal vaginal pH is 3.8 to 4.5. Bacterial vaginosis usually causes the vaginal pH to rise above 4.5.
• Pap test. Bacterial vaginosis may be detected during routine Pap testing. However, Pap testing is not a standard test to diagnose bacterial vaginosis.
• Gram stain. A sample of the vaginal discharge is placed on a microscope slide. A special dye is applied to the slide, causing certain types of bacteria (Gram-positive bacteria) to turn a shade of purple while coloring others (Gram-negative bacteria) pink. In bacterial vaginosis, Gram-negative bacteria, especially Gardnerella vaginalis, are most common.
• Oligonucleotide probes. This test detects the genetic material (DNA) of bacterial vaginosis bacteria. Oligonucleotide probe testing is very accurate but is not routinely available in most labs.

The presence of clue cells, an increased vaginal pH, and a positive whiff test are enough evidence to treat for bacterial vaginosis.

Treatment options for bacterial vaginosis include:

• Watchful waiting. In about 1 out of 4 women, bacterial vaginosis symptoms resolve on their own.¹ This happens when the vaginal lactobacilli organisms increase to their normal levels, and other bacteria levels drop.
• Antibiotic medication (oral or vaginal). Antibiotics can kill the problem bacteria causing bacterial vaginosis symptoms but sometimes don't reverse the underlying cause. Therefore, symptoms recur in about 1 out of 3 of women after antibiotic treatment.²

For some women, bacterial vaginosis goes away without treatment. But, when it does not go away even with treatment, bacterial vaginosis is frustrating and troublesome. And, it can lead to preterm labor if you have it during pregnancy. If present during pelvic surgery or invasive vaginal procedures, bacterial vaginosis makes the reproductive tract vulnerable to infection or inflammation, which has been linked to such problems as pelvic inflammatory disease (PID).⁵ Therefore, your health professional will test and treat you with antibiotics for bacterial vaginosis if you are:

• Having persistent symptoms.
• Pregnant and have symptoms.
• Pregnant with no symptoms, but have a history of preterm labor (before 37 completed weeks of pregnancy) that may have been related to infection.⁷
• Planning to have a hysterectomy or surgical abortion. Treating bacterial vaginosis with antibiotics beforehand greatly lowers your risk of getting a serious infection afterward. Other procedures linked to bacterial vaginosis-related infection include endometrial biopsy, intrauterine device (IUD) placement, cesarean section, dilation and curettage (D&C), and hysterosalpingography, an X-ray test that examines the inside of the uterus, the fallopian tubes, and surrounding area. ⁵

Talk to your health professional about whether screening is right for you.

What To Think About

If you are planning to become pregnant and have a history or symptoms of bacterial vaginosis, talk to your health professional about screening and treatment before you start a pregnancy.

For decades, some women have used Lactobacillus acidophilus in yogurt or supplements to treat bacterial vaginosis. However, experts now know that dairy lactobacillus is not the kind that normally lives in the vagina. This is why dairy lactobacillus does not work for bacterial vaginosis. But, researchers have found that two different types of lactobacillus—L. crispatus and L. jensenii—are most commonly found in a healthy vaginal environment. Research is now focusing on using these types of lactobacilli in capsules.⁸

If your health professional finds other problems during the exam, such as a possible sexually transmitted disease (STD), appropriate treatment will be recommended.

Since it probably is not passed between a man and woman, treating a male sex partner or partners will not help cure bacterial vaginosis.⁵ But, for a woman with a female sex partner, it is possible that bacterial vaginosis is passed back and forth, although this is not yet proven. In this case, treating both partners may help.

To help prevent bacterial vaginosis:

• Limit the number of your sex partners. Multiple sex partners increase your risk of developing bacterial vaginosis by changing the normal environment of the vagina.
• Avoid douching.

Bacterial vaginosis may be passed between women during sexual contact. If you have a female sexual partner, you may benefit from using condoms with or careful washing of shared sex items.⁹

Bacterial vaginosis is not passed between men and women and is not considered a sexually transmitted disease (STD). (But if you are exposed to an STD while you have bacterial vaginosis, you are more likely to be infected by that disease.¹)

It is always important to practice safe sex to prevent sexually transmitted diseases, whether or not you have bacterial vaginosis. Preventing an STD is easier than treating an infection after it occurs.

For decades, some women have used Lactobacillus acidophilus in yogurt or supplements to treat bacterial vaginosis. However, dairy lactobacillus does not work for bacterial vaginosis. This is because dairy lactobacillus is not the kind of bacteria that normally live in the vagina.⁹

Researchers are studying the two different types of lactobacillus—L. crispatus and L. jensenii—that are most commonly found in a healthy vagina.⁸ Hopefully, these lactobacilli will prove to be an effective treatment for bacterial vaginosis.

Antibiotics are the standard treatment for bacterial vaginosis. Metronidazole (Flagyl; MetroGel) and clindamycin (Cleocin; Clindesse) are the first-choice medications for treating bacterial vaginosis. For women who cannot tolerate metronidazole, the broad-spectrum antibiotic clindamycin is a good option.

These antibiotics can be given by mouth (orally) or inserted into the vagina. During pregnancy, women who are high-risk for preterm labor are advised to avoid vaginal application of any treatment. Some doctors recommend that all pregnant women avoid vaginal treatments.

Studies generally indicate that vaginal antibiotics are as effective as oral antibiotics for treating bacterial vaginosis.¹⁰ Medications inserted into the vagina cause fewer side effects than oral medications, although they can make you vulnerable to vaginal yeast infection.

When considering treatment for bacterial vaginosis, ask your health professional whether you should:

• Use oral medication or medication inserted into the vagina. Some women prefer taking pills to using a vaginal medication.
• Avoid having sex during treatment.
• Continue treatment during your menstrual period. Medication placed in your vagina is more difficult to use during your period, but your health professional may recommend continuing treatment during this time.
• Avoid drinking alcohol during treatment with metronidazole. This medicine can cause severe nausea and vomiting if you drink alcohol when taking it. Clindamycin does not.

The mineral oil in clindamycin cream or ovules can cause latex condoms or diaphragms to fail. This is also true for metronidazole cream and tablets (the gel is fine for use with condoms and diaphragms). Don't trust barrier methods of birth control when using this type of vaginal medication.

There is no surgical treatment for bacterial vaginosis.

For decades, some women have used Lactobacillus acidophilus in yogurt or supplements to treat bacterial vaginosis. However, researchers now know that dairy lactobacillus does not work for bacterial vaginosis. This is because dairy lactobacillus is not the kind of bacteria that normally lives in the vagina. But, researchers have found two different types of lactobacillus—L. crispatus and L. jensenii—that are most commonly found in a healthy vaginal environment. Research is now focusing on using these types of lactobacilli in capsules.⁸

Organizations

• Abnormal Pap Test
• Exposure to Sexually Transmitted Diseases
• Pap Test
• Pelvic Inflammatory Disease
• Preterm Labor
• Trichomoniasis
• Vaginal Wet Mount
• Vaginal Yeast Infections

Citations

1. Koumans EH, et al (2002). Indications for therapy and treatment recommendations for bacterial vaginosis in nonpregnant and pregnant women: A synthesis of data. Clinical Infectious Diseases, 35(Suppl 2): S152–S172.

2. Joesoef MR, Schmid G (2005). Bacterial vaginosis. Clinical Evidence (13): 1968–1978.

3. Hillier S, Holmes KK (1999). Bacterial vaginosis. In KK Holmes et al., eds., Sexually Transmitted Diseases, 3rd ed., pp. 572–574. New York: McGraw-Hill.

4. Leitich H, et al. (2003). Bacterial vaginosis as a risk factor for preterm delivery: A meta-analysis. American Journal of Obstetrics and Gynecology, 189(1): 139–147.

5. Centers for Disease Control and Prevention (2002). Diseases characterized by vaginal discharge section of Sexually transmitted diseases treatment guidelines. MMWR, 51(RR-6): 42–48.

6. Fethers K, et al. (2000). Sexually transmitted infections and risk behaviours in women who have sex with women. Sexually Transmitted Infections, 76(5): 345–349.

7. U.S. Preventive Services Task Force (2002). Screening for bacterial vaginosis in pregnancy: Recommendations and rationale. American Family Physician, 65(6): 1147–1150.

8. Kessel KV, et al. (2003). Common complementary and alternative therapies for yeast vaginitis and bacterial vaginosis: A systematic review. Obstetrical and Gynecological Survey, 58(5): 351–358.

9. Marrazzo JM (2004). Evolving issues in understanding and treating bacterial vaginosis. Expert Review of Anti-Infective Therapy, 2(6): 913–922.

10. Leitich H, et al. (2003). Antibiotic treatment of bacterial vaginosis in pregnancy: A meta-analysis. American Journal of Obstetrics and Gynecology, 188(3): 752–758.

Other Works Consulted

• Abramowicz M (2007). Treatment guidelines: Drugs for sexually transmitted infections. Medical Letter on Drugs and Therapeutics, 5(61): 81– 88.

• Ainbinder SW, et al. (2007). Sexually transmitted diseases and pelvic infections. In AH DeCherney et al., eds., Current Diagnosis and Treatment Obstetrics and Gynecology, 10th ed., p. 670. New York: McGraw-Hill Medical Publishing Division.

• Mazdisnian F (2007). Benign disorders fo the vulva and vagina. In AH DeCherney et al., eds., Current Diagnosis and Treatment Obstetrics and Gynecology, 10th ed., pp. 598–622. New York: McGraw-Hill Medical Publishing Division.

• Abramowicz M (2007). Tinidazole (Tindamaz) - A new option for treatment of bacterial vaginosis. Medical Letter on Drugs and Therapeutics, 49(1269): 73–74.

• American College of Obstetricians and Gynecologists (2006). Vaginitis. ACOG Practice Bulletin No. 72. Obstetrics and Gynecology, 107(5): 1195–1206.

• Eckert LO, Lentz GM (2007). Infections of the lower genital tract. In VL Katz et al., eds., Comprehensive Gynecology, 5th ed., pp. 569–606. Philadelphia: Mosby Elsevier.

• Soper DE (2007). Genitourinary infections and sexually transmitted diseases. In JS Berek, ed., Novak's Gynecology, 14th ed., pp. 541–559. Philadelphia: Lippincott Williams and Wilkins.