Maternity Care Calendar and Guidelines: Screening for Bacterial Vaginosis (BV)

Current MCC Guideline(1998):

screening by gram stain or Amsel criteria^* for bacterial vaginosis in women at risk for preterm labour or PROM or symptomatic women
in plain font
listed under "Investigations" for early pregnancy

Amsel Criteria: Need 3 of:
1. homogeneous white or gray noninflammatory vaginal discharge
2. presence of clue cells
3. pH of vaginal secretions> 4.7
4. amine (fishy) odor of vaginal discharge before or after addition of 10% KOH

Summary of Evidence:
The US Preventive Services Task Force (USPSTF) completed a report on screening for bacterial vaginosis (BV) in 2001.¹ They made the following recommendations:

The evidence is insufficient to recommend for or against routinely screening high-risk pregnant women for bacterial vaginosis (I recommendation) **
there is fair evidence to recommend against routinely screening average-risk asymptomatic pregnant women for BV (D recommendation)

Notes** ¹:

screening for BV is an option for women with a history of preterm delivery. For women with a previous preterm delivery, the inconsistent results of well-done studies prevent a clear recommendation for or against screening. The studies demonstrating a benefit of screening and treatment were performed among populations of women especially at high risk (35% to 57%)of preterm birth.
optimal screening test and timing of screening is not certain. Currently the accepted clinical criteria for BV are the Amsel criteria. (see above). In the 3 trials demonstrating a benefit of screening high risk women, screening was done in the 2^nd trimester (13-34 weeks)
optimal treatment regimen is unclear. In the trials showing a benefit of screening and treatment, various regimens of oral metronidazole or oral metronidazole and erythromycin were used.
treatment is appropriate for symptomatic pregnant women

Recommendations of Others:
A systematic review of randomized controlled trials assessing the effects of antibiotic treatment of BV in pregnant women was completed for the Cochrane Collaboration in 1998.² The reviewers concluded, "the current evidence does not support screening and treating all pregnant women for BV to prevent preterm birth. For women with a history of preterm birth, there is some suggestion that detection and treatment of asymptomatic BV early in pregnancy may prevent some of these women from having a further preterm birth. Whether this leads to an improvement in neonatal well-being is unknown."

Recommendations from the Centers for Disease Control and Prevention are that "evaluation for BV may be conducted at the first prenatal visit for asymptomatic patients who are at high risk for preterm labor (e.g. previous preterm delivery). Current evidence does not support routine testing for BV."³ Symptomatic pregnant women should be treated. The report states that BV can be diagnosed by use of clinical criteria (see Amsel criteria above) or gram stain. Culture of Gardnerella vaginalis is not recommended for diagnosis as it is not specific.

The CDC recommends two treatment regimens for BV in pregnancy:

Metronidazole 250 mg orally three times a day for 7 days*
or
clindamycin 300 mg orally twice a day for 7 days

They note that existing data do not support the use of topical agents during pregnancy. Evidence from 3 trials suggests an increase in adverse events in neonates after the use of clindamycin cream. No teratogenic effects are associated with metronidazole use in pregnancy. Screening and treatment (if conducted) should be preformed at the first prenatal visit. A follow-up evaluation 1 month after treatment should be considered.
*This dose is also recommended by other authors.⁴

In 1998, the American College of Obstetricians and Gynecologists (ACOG), developed a committee opinion stating that screening for BV may be considered in women at high risk for preterm labor. Women with a positive test or symptoms of BV should be treated with oral metronidazole.⁵

In 1997, the Society of Obstetricians and Gynaecologists of Canada (SOGC) produced a committee opinion on bacterial vaginosis.⁶ They concluded that "it seems prudent to suggest that patients at risk for preterm delivery and premature rupture of membranes be treated.

In a 2002 Motherisk Update⁷, the authors conclude that there is no benefit from screening or treating pregnant women at average risk of BV. It is not clear if treating pregnant women at high risk is beneficial. If treating BV, the drugs of choice are oral or intravaginal gel metronidazole or oral clindamycin. Both drugs are safe to use throughout pregnancy.

Conclusions:
The new guideline on the MCC will be as follows:

consider screening by gram stain or Amsel Criteria* for bacterial vaginosis in women at increased risk for preterm labour or symptomatic women
only symptomatic women will be bolded
the recommendations for screening women at increased risk for preterm labour will be in plain font as it is an I recommendation
*Amsel criteria will be available on the MCC website, but will be removed from the guidelines checklist due to space constraints
It will be listed under "investigations" suggested for early pregnancy, following other tests requiring a speculum examination (the PAP, chlamydia and gonorrhea tests) for convenience. The optimal time to screen high-risk patients remains uncertain. The USPSTF notes that the 3 trials demonstrating a benefit were done in the second trimester. The review for the Cochrane Collaboration discusses screening "early in pregnancy" for high-risk women. The CDC report states that screening (if conducted) and treatment should be performed at the first prenatal visit, while the ACOG report suggests screening and treating after the first trimester.

Reviewer: Colleen Kirkham, MD, CCFP November 2002

1/30/03 11:46 AM

¹ U.S. Preventive Services Task Force. Screening for Bacterial Vaginosis: Recommendations and Rationale. Am J Prev Med 2001;20:59-61
² Brocklehurst P, Hannah M, McDonald H. Interventions for treating bacterial vaginosis in pregnancy (Cochrane Review). In: The Cochrane Library, Issue 4, 2002. Oxford: Update Software
³ Centers for Disease Control and Prevention. Sexually transmitted disease treatment guidelines 2002. MMWR 2002;51 (No. RR-6):1-84
⁴ Joesoef MR, Schmid GP, Hillier SL. Bacterial Vaginosis: Review of treatment options and potential clinical indications for therapy. Clinical Infectious diseases 1999;28(Suppl 1)S57-65.
⁵ Bacterial vaginosis screening for prevention of preterm delivery. Committee Opinion No. 198. International Journal of Gynecology & Obstetrics 1998;61:311-12.
⁶ SOGC Committee Opinion: Bacterial vaginosis. No. 14, March 1997.
⁷ Einarson A, Koren G. Motherisk Update: Bacterial vaginosis during pregnancy. Canadian Family Physician 2002;48:877-8.