Bacterial Vaginosis

Bacterial vaginosis (BV) is a common form of infectious vaginitis caused by the polymicrobial proliferation of Gardnerella vaginalis, Mycoplasma hominis, and other anaerobes. It is associated with loss of normal lactobacilli. bacterial vaginosis accounts for at least 10% and as many as 50% of all cases of infectious vaginitis in women of childbearing age. Determining the presence of bacterial vaginosis can be difficult, however, because as many as 75% of women are asymptomatic.


Some or all of these symptoms may be present in women with bacterial vaginosis.

  • • Milky, homogenous discharge
  • • Possible vaginal irritation
  • • Malodorous vaginal discharge (characteristic “fishy” odor) bacterial vaginosis is also commonly asymptomatic.


Diagnosis is based on the Amstel criteria, which is considered 90% accurate with three or four of the following findings: the presence of milky, homogenous discharge, vaginal pH greater than 4.5 positive whiff test (“fishy” odor to the vaginal discharge), and the presence of clue cells on light microscopy of vaginal fluid. Odor is a symptom that is frequently associated with bacterial vaginosis, due to amines produced from the breakdown products of amino acids produced by Gardnerella vaginalis in the presence of anaerobic bacteria. This also results in a rise in vaginal pH.

Risks for Developing Bacterial Vaginosis

Numerous factors, described in Table Factors Associated with the Development and Pathophysiology of Bacterial Vaginosis, are associated with the development of bacterial vaginosis. It is uncertain whether bacterial vaginosis is a sexually transmitted disease. The prevalence is higher in women with multiple sexual partners and in women seeking the services of STD clinics. Treatment of sexual partners of women with the infection has not definitely proved to be beneficial; however, urethral smears of male partners often show typical bacterial vaginosis morphocytes.

Factors Associated with the Development and Pathophysiology of Bacterial Vaginosis

Type Of Risk FactorExamples
Personal risk factorsUse of: tampons, sponges, douches, intrauterine devices, sex toys Sexual practices: new or multiple sexual partners, receptive oral sex, latex condoms, contraceptive methods such as cervical cap, IUD, or spermicide Other risk factors: antibiotic use, oral contraceptives, smoking
Microbial factorsInitiating infectious agents; possibly a sexually transmitted infection Decline in lactobacillus numbers Rise in pH Lack of hydrogen peroxide produces lactobacillus strains

Risks Associated with Bacterial Vaginosis

BV in pregnancy appears to be a risk factor for second trimester miscarriage, premature rupture of the membrane and premature labor, chorioamnionitis, and post-cesarean and postpartum endometritis. Women with bacterial vaginosis have an increased incidence of abnormal Pap smears, pelvic inflammatory disease (PID), and endometritis. Further, the presence of bacterial vaginosis in women undergoing invasive gynecologic procedures may increase the risk of serious infection including vaginal cuff cellulitis, PID, and endometrirtis. Eliminating bacterial vaginosis appears to decrease the risk of acquiring HIV infection; thus, it is suggested that women with bacterial vaginosis be treated regardless of whether they are symptomatic.

Conventional Treatment of Bacterial Vaginosis

CDC guidelines recommend the treatment of all women with symptomatic bacterial vaginosis. Conventional treatment of bacterial vaginosis is metronidazole (Flagyl) orally or vaginally (Metro-gel), or Clindamycin. Proper treatment typically results in an 80% cure rate at 4 weeks, with recurrence rates of 15% to 50% in 3 months. Treatment failure may be caused by lack of successful recolonization of hydrogen peroxide producing strains of lactobacillus, antibiotic resistance, and possibly reinfection by male partners.

Metronidazole is also the prescribed treatment during pregnancy; however, it is contraindicated in the first trimester because of theoretic risks of teratogenicity. Thus, many pregnant women prefer to avoid exposure altogether. Clindamycin is used as an alternative.

Evidence on the use of antibiotics in pregnancy to reduce the risk of preterm labor and its associated morbidities is somewhat conflicting. A Cochrane review concluded that no evidence supports the screening of all women for bacterial vaginosis, and Guidelines of the American College of Obstetricians and Gynecologists (ACOG) also does not recommend screening in asymptomatic patients. According to a recent (2005) systematic review, no evidence supports the use of antibiotic treatment for either bacterial vaginosis or Trichomonas vaginalis (see later in this section) for reducing preterm birth in low- or high-risk women. Nonetheless, CDC Guidelines (2002) still recommend treatment of all pregnant women with Metronidazole or Clindamycin.