Bacterial Vaginosis During Pregnancy

Bacterial vaginosis pregnancy

Note: The Pregistry website includes expert reports on more than 2000 medications, 300 diseases, and 150 common exposures during pregnancy and lactation. For the topic Bacterial Vaginosis, go here. These expert reports are free of charge and can be saved and shared.


Bacterial vaginosis (BV) is a condition in which there is discharge from the vagina due to overgrowth of bacterial species that do not usually dominate the community of microorganisms known as the vaginal microbiota. The overgrowth of those species is caused by a normally dominant bacterial group, called Lactobacillus, not thriving as it should.  The atypical bacteria thus grow to take the place of Lactobacillus. The atypical bacteria of the vagina are anaerobic, meaning that they thrive without oxygen, although some are facultative, meaning that they can thrive with or without oxygen. If you have BV, you may or may not experience symptoms.

BV is the most common lower genital tract infection in women of reproductive age. The condition may occur in up to 32 percent of pregnancies. Although doctors do not think that BV is a sexually transmitted infection, women who have had multiple sex partners have an elevated risk of developing BV compared to other women. Vaginal douching also may increase the BV risk.

Typically, BV shows up as a discharge with a strong, fishy odor. This is usually what alerts a woman that she should get medical help. During pregnancy, BV is similar to how it is in non-pregnant women, but negative consequences are more likely in pregnant women. It is possible to screen women for BV with tests of vaginal specimens, but usually doctors don’t do this. Thus, usually BV is not recognized until you report the discharge.

When you visit your doctor complaining of the foul smelling discharge, your doctor will perform a pelvic exam. The pH of your vagina will then be tested. If the vaginal pH is elevated, meaning higher than 4.5, it raises the suspicion that you may have BV. A sample of vaginal secretions will be viewed under a microscope to see if there are clear cells, vaginal cells covered with bacteria, which give the cells a particular appearance. There also are molecular tests to reveal particular genetic sequences of the atypical bacteria that have replaced the normal vaginal bacteria.

Bacterial vaginosis is the most common lower genital tract infection in women of reproductive age. The condition may occur in up to 32 percent of pregnancies.

In addition to foul smelling discharge, BV can be a problem during pregnancy because it increases the risk of spontaneous abortion (miscarriage), preterm labor and preterm delivery, 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 fetus). BV also may increase the risk of pelvic inflammatory disease and can facilitate the spread of human immunodeficiency virus (HIV) from women who are HIV positive.

The preferred treatment for BV is a medication called metronidazole, which you take as a pill twice per day for a week. Metronidazole is particularly effective because it kills the atypical bacteria that have taken over, but without harming the normal Lactobacillus that needs to recover. An alternative to metronidazole is clindamycin, which also can be taken as a pill or it can be applied as a vaginal cream. Both medications are safe during pregnancy. Metronidazole also is the treatment choice for treating BV in mothers who are breastfeeding, as it is safe for nursing infants.

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

Leave a Reply