Bacterial Vaginosis and Pregnancy

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About 25% of pregnant women are diagnosed with bacterial vaginosis (BV). BV is a vaginal infection that occurs when there is an imbalance in the normal, healthy vaginal flora (microorganisms). When this happens, the “bad” bacteria outweigh the “good” bacteria that normally live in the vagina. 

The most common symptoms of bacterial vaginosis are a strong “fishy” smelling discharge and an increased amount of vaginal discharge.

BV is easily treated with antibiotics. However, left untreated in pregnancy, BV can increase your infant’s risk of a premature (early) birth or a low-birth-weight baby.  

This article reviews the symptoms, causes, risk factors, complications, prevention, and treatment of bacterial vaginosis during pregnancy. 

Pregnant woman speaking with a healthcare provider about bacterial vaginosis.

SDI Productions / Getty Images

What Are the Symptoms of Bacterial Vaginosis?

Sometimes BV does not cause symptoms. For some women, symptoms are intermittent, meaning they come and go. When symptoms are present, the most common are:

  • A strong odor: BV often comes with a foul-smelling vaginal discharge. It may be stronger after vaginal sexual intercourse or menstruation.
  • Increased vaginal discharge: BV can also cause an increase in vaginal discharge. It is usually a thin (and sometimes foamy) gray, greenish, yellow, or white. 

Less common symptoms of BV include:

  • Burning or itching in the vagina
  • Burning with urination
  • Itching around the outside of the vagina
  • Bleeding after intercourse

How BV Is Diagnosed

To diagnose BV, your healthcare provider will take a medical history and perform a physical exam and a vaginal exam. This is similar to a pelvic exam and Pap smear (the exams you get during routine gynecological wellness checks). 

Three of the following four criteria must be met to diagnose bacterial vaginosis:

  • A pH above 4.5
  • Thin, increased vaginal discharge
  • Fishy odor when 10% potassium solution is added to the discharge sample
  • 20% or greater clue cells (fuzzy-looking cells that indicate bacteria) when the discharge is examined under a microscope

Your healthcare provider will also likely test for sexually transmitted infections (STIs) during this appointment.

What Causes Bacterial Vaginosis?

Healthy vaginas have naturally occurring bacteria called normal flora. The healthy bacteria and vaginal discharge keep the vagina clean and free from infection. 

Bacterial vaginosis occurs when the healthy balance of bacteria in the vagina is disrupted. The “bad” bacteria take over the “good” bacteria. 

While BV is not an STI, it can result from sexual activity. 

Risk Factors For Bacterial Vaginosis

The following factors increase your risk of BV:

  • Douching regularly 
  • Using fragranced feminine hygiene products 
  • Having multiple sex partners
  • Not using condoms
  • Smoking
  • Having sex with women (typically, both women get the infection)
  • Pregnancy (due to hormone changes)
  • Having an intrauterine device (IUD) (this is a small risk with limited evidence)

Due to various reasons, there are more recorded cases of BV in Black and Hispanic populations than in other groups in the United States.

What Are the Possible Complications of Bacterial Vaginosis?

While BV is typically mild, it’s essential to treat it, especially during pregnancy. When left untreated, there are rare but serious complications associated with BV, including:

  • Preterm delivery or low birth weight: Having BV during pregnancy increases the risk of having your baby too early. It also increases the risk of the baby having a low birth weight.
  • STIs: BV increases your risk of getting STIs, including human immunodeficiency virus (HIV), herpes simplex virus (HPV), chlamydia, or gonorrhea.
  • Pelvic inflammatory disease (PID): PID is an infection of the uterus, ovaries, and fallopian tubes
  • Infertility: Untreated BV can lead to PID, increasing the risk of infertility or less success with fertility treatments.
  • Increased risk of infection after gynecologic surgeries: BV is a risk factor for developing infections after gynecological surgeries such as hysterectomies (surgical removal of the uterus). 

How Is Bacterial Vaginosis Treated During Pregnancy?

Even if BV symptoms are mild, it’s essential to seek treatment to prevent complications. During pregnancy, BV is typically treated with one of the following antibiotics: 

  • Flagyl (metronidazole)
  • Clindacin, Cleocin, Clindesse (clindamycin)

Your healthcare provider may prescribe pills to be taken by mouth or a gel or cream inserted intravaginally (in the vagina). Antibiotic treatment for BV is usually prescribed for five to seven days. It’s best to abstain from sexual contact until the end of treatment and your symptoms have resolved. 

Are Metronidazole and Clindamycin Safe While Pregnant or Breastfeeding?

Research studies have not found concerns with taking metronidazole or clindamycin while pregnant or breastfeeding. This includes in the first trimester of pregnancy. 

Tinidazole is an antibiotic prescribed for nonpregnant people. It has not been studied in pregnancy. Pregnant people should avoid tinidazole.

Healthcare providers often prefer vaginal cream over pills for people who are breastfeeding whenever possible. This is because the medication does not get distributed throughout the body and breast milk as much as oral medication.

Your healthcare provider may also consider the following to treat BV:

Intimate partners who also are women should see their healthcare provider. This is because BV can spread between female sex partners. Both women typically get the infection, and partners may need treatment even if they don’t have symptoms. 

Male partners typically do not need medical treatment. Most research indicates treating your male partner does not help to prevent your recurrent BV. This may change if further studies show that treatment is helpful. 

Recurring BV During Pregnancy

Sometimes healthcare providers prescribe both oral and vaginal medications for you to take at the same time. This is especially true if the infection is recurring (comes back). With recurring infections, healthcare providers may increase the medication's dose and duration (time). They may also prescribe a maintenance dose of vaginal cream to prevent it from returning. 

How to Prevent Bacterial Vaginosis 

While BV is not an STI, it can be passed during sexual activity. The following decreases your risk of bacterial vaginosis related to sexual activity: 

  • Use barrier devices such as condoms and dental dams.
  • Limit the number of sexual partners or abstain from sexual activity.
  • Avoid vaginal contact with anything that has touched your anus.
  • Clean sex toys after every use.

The following tips can also reduce the risk of bacterial vaginosis:

  • Avoid fragranced soaps, sprays, or feminine hygiene products.
  • Avoid vaginal douching.
  • Wear breathable underwear made from fabric such as cotton.
  • Wipe from front to back after you use the restroom.
  • Quit smoking.


Bacterial vaginosis (BV) is a vaginal infection that occurs when there is an imbalance in the normal vaginal flora. With BV, the unhealthy bacteria outweigh the healthy bacteria in the vagina. 

The most common symptoms of bacterial vaginosis are a pungent “fishy” smelling discharge and an increase in vaginal discharge.

BV is treated with antibiotics that are safe to take during pregnancy. Untreated BV can increase your risk of a premature birth or a low-birth-weight baby. While BV is not a sexually transmitted infection (STI), it is related to sexual activity. Safer sex practices can help reduce the risk of getting BV.

A Word From Verywell

While bacterial vaginosis is common, having a vaginal infection during pregnancy can be unnerving. Women are often concerned it will harm their unborn babies. Fortunately, BV is easily treated with safe antibiotics during pregnancy and while breastfeeding. If you have any symptoms, call your healthcare provider as early diagnosis and treatment decrease the risk of complications such as premature delivery or low birth weight.   

Frequently Asked Questions

  • Does bacterial vaginosis need to be treated in pregnancy?

    Yes, it’s important to treat BV during pregnancy. Left untreated, BV can cause complications such as preterm delivery or a low-birth-weight baby. 

  • How do they test for BV during pregnancy?

    Your healthcare provider will talk to you about your symptoms and do a vaginal exam. During the exam, they will take a sample of the vaginal discharge with a long cotton-tipped swab. They may also use a pH strip to test the acidity level of the vaginal fluid. 

  • Will I be screened for BV if I don’t have any symptoms?

    While this topic is still controversial in the scientific community, the U.S. Preventive Services Task Force (USPSTF) recommends against screening for bacterial vaginosis for women at low risk for preterm labor. However, your healthcare provider may suggest screening if you have symptoms or are at high risk for preterm birth. 

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Planned Parenthood. What is bacterial vaginosis?

  3. Sim M, Logan S, Goh L. Vaginal discharge: evaluation and management in primary care. Singapore Med J. 2020;61(6):297-301. doi:10.11622/smedj.2020088

  4. Ibrahim A. Comparison of in vitro activity of metronidazole and garlic-based product (tomex®) on trichomonas vaginalis. Parasitol Res. 2013;112(5):2063-2067. doi:10.1007/s00436-013-3367-6

  5. Eunice Kenedy Shriver National Institute of Child Health and Human Development (NIH). How do healthcare providers diagnose bacterial vaginosis (bv)?

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Additional Reading

By Brandi Jones, MSN-ED RN-BC
Brandi is a nurse and the owner of Brandi Jones LLC. She specializes in health and wellness writing including blogs, articles, and education.