Bacterial Vaginosis


The information provided below is for readers based in the United States of America. Readers outside of the United States of America should seek the information from local sources.

What is bacterial vaginosis?

Bacterial vaginosis (BV) is a condition characterized by a discharge from the vagina resulting from overgrowth of various species of bacteria that do not typically dominate the vaginal microbiota, the various microbial species that inhabit your vagina. This happens because species of Lactobacillus bacteria, which normally dominate the vaginal microbiota, are not thriving as they usually do, so the atypical bacteria grow and thrive to take their place. These atypical vaginal bacteria tend to thrive without as much oxygen (anaerobic bacteria and facultative bacteria). While BV can be asymptomatic (present without producing symptoms), typically it appears with a discharge that has a strong, fishy odor, which usually is the reason why women with BV seek help. The features of BV are the same for pregnant women as they are for non-pregnant women, but during pregnancy the potential for negative consequences is higher. Although it is possible to screen women for BV by testing vaginal samples, generally this is not done, and typically the condition is not recognized until the women report the discharge.

How common is bacterial vaginosis in pregnancy?

BV is the most common infection in the lower genital tract in women of reproductive age. Reports of the percentage of women who have BV vary widely. However, among women with some form of lower genital tract infection, BV has been reported to account for about 40 50 percent of cases. Reports of BV in pregnancy suggest that BV could be present in as many as 32 percent of pregnancies. Although BV is not considered a sexually transmitted infection, the risk of developing BV is elevated in women who have had multiple sex partners. Vaginal douching also is thought to increase the risk of developing BV.

How is bacterial vaginosis diagnosed?

BV is diagnosed through a series of procedures beginning with your report of the presence of a foul-smelling discharge, followed by your doctor performing a pelvic exam. The pH of your vagina is tested to see if it is elevated, meaning higher (more alkaline) than 4.5. Your vaginal secretions will be sampled and tested under the microscope for the presence of what is called clear cells, which are vaginal cells covered with bacteria, which give the cells a very distinct look. Additionally, there are molecular tests that look for particular genetic sequences to reveal the identity of the atypical bacteria that have replaced your normal vaginal bacteria.

Does bacterial vaginosis cause problems during pregnancy?

Yes. In addition to causing an unpleasant, foul-smelling vaginal discharge, BV that develops during pregnancy appears to increase the risk of spontaneous abortion (miscarriage), preterm labor and preterm delivery, preterm premature rupture of membranes (your water breaks too early, which can be a trigger for preterm labor), and chorioamnionitis (infection and inflammation of the membranes surrounding the developing baby). Having BV also can increase your risk for pelvic inflammatory disease. Additionally, BV can make it easier to spread human immunodeficiency virus (HIV) if you have that.

Does bacterial vaginosis cause problems for the baby?

BV can trigger spontaneous abortion (miscarriage), and also can trigger preterm labor and preterm delivery, both directly and by causing any of the following other problems: preterm premature rupture of membranes, chorioamnionitis, endometritis, and surgical wound infections (if you have had surgery).

What to consider about taking medications when you are pregnant:

  • The risks to yourself and your baby if you do not treat the bacterial vaginosis
  • The risks and benefits of each medication you use when you are pregnant
  • The risks and benefits of each medication you use when you are breastfeeding

What should I know about using medication to treat bacterial vaginosis during pregnancy?

The treatment of choice for BV is metronidazole, which is given as a pill taken twice per day for one week. This drug is particularly useful because it destroys the atypical bacteria that have taken over, but it does not harm the normal Lactobacillus that you want to grow back. An alternative is clindamycin, which can be taken orally, but also can be applied as a vaginal cream. Both of these medications are considered safe during pregnancy.

Who should NOT stop taking medication for bacteria vaginosis in pregnancy?

The only reason to stop a BV medication is that you prove to be allergic to the medication, in which case, you must be switched to a different medication.

What should I know about choosing a medication for bacterial vaginosis in pregnancy?

You may find Pregistrys expert reports about the individual medications to treat bacterial vaginosis here. Additional information can also be found in the sources listed at the end of this report.

What should I know about taking a medication for bacterial vaginosis when I am breastfeeding?

Metronidazole and clindamycin are both considered to be very safe in nursing mothers.

What alternative therapies are there besides medications to treat bacterial vaginosis during pregnancy?

Medication is the key to treating BV. Given the potential for dangerous complications from BV both for you and your baby, there really is no alternative to medication. To prevent further BV, don’t douche – your vagina keeps itself clean without needing any outside help. 

What can I do for myself and my baby when I have bacterial vaginosis during pregnancy?

Reassure yourself that with treatment the chances of complications from BV are reduced dramatically. Take your medication as directed and stay in contact with your physician.

Resources for bacterial vaginosis during pregnancy:

For more information about bacterial vaginosis during pregnancy, contact (800-994-9662 [TDD: 888-220-5446]) or read the following articles:


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Last Updated: 28-02-2020
General information

It is very common for women to worry about having a miscarriage or giving birth to a child with a birth defect while they are pregnant. Many decisions that women make about their health during pregnancy are made with these concerns in mind.

For many women these concerns are very real. As many as 1 in 5 pregnancies end in a miscarriage, and 1 in 33 babies are born with a birth defect. These rates are considered the background population risk, which means they do not take into consideration anything about the health of the mom, the medications she is taking, or the family history of the mom or the baby’s dad. A number of different things can increase these risks, including taking certain medications during pregnancy.

It is known that most medications, including over-the-counter medications, taken during pregnancy do get passed on to the baby. Fortunately, most medicines are not harmful to the baby and can be safely taken during pregnancy. But there are some that are known to be harmful to a baby’s normal development and growth, especially when they are taken during certain times of the pregnancy. Because of this, it is important to talk with your doctor or midwife about any medications you are taking, ideally before you even try to get pregnant.

If a doctor other than the one caring for your pregnancy recommends that you start a new medicine while you are pregnant, it is important that you let them know you are pregnant.

If you do need to take a new medication while pregnant, it is important to discuss the possible risks the medicine may pose on your pregnancy with your doctor or midwife. They can help you understand the benefits and the risks of taking the medicine.

Ultimately, the decision to start, stop, or change medications during pregnancy is up to you to make, along with input from your doctor or midwife. If you do take medications during pregnancy, be sure to keep track of all the medications you are taking.

Medications for Bacterial Vaginosis

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