Screening Pregnant Women for Bacterial Vaginosis Not Recommended

News Author:
Laurie Barclay, MDCME

Author: Laurie Barclay, MD

February 4, 2008 — The US Preventive Services Task Force (USPSTF) recommends against clinicians screening for bacterial vaginosis in asymptomatic pregnant women who are at low risk for premature delivery, according to the results of an updated review and guidelines reported in the February 5 issue of the Annals of Internal Medicine.

"The associations between bacterial vaginosis and adverse pregnancy outcomes, such as preterm delivery, are well documented," the USPSTF writes. "Good-quality evidence indicates that screening tests (the Amsel clinical criteria or Gram stain) can detect bacterial vaginosis."
The USPSTF review suggests that there is good evidence that screening for bacterial vaginosis does not benefit pregnant women at low risk for premature delivery, and the expert USPSTF panel therefore recommends against screening low-risk women for bacterial vaginosis.
Among women of reproductive age, bacterial vaginosis is the most common lower genital tract syndrome, and it has been associated with premature births or low birthweight. Because it is easy to screen for and treat bacterial vaginosis, some experts have recommended screening all pregnant women for this condition. However, in this review, the USPSTF finds insufficient evidence to recommend either for or against screening for the syndrome in pregnant women at high risk for premature delivery.

The USPSTF identified new evidence that addressed gaps identified in the previous 2001 USPSTF recommendation, and they weighed the benefits and harms of screening for bacterial vaginosis in pregnancy in light of the new evidence. A search of MEDLINE, Cochrane Library databases, and the Database of Abstracts of Reviews of Effects identified published literature on this topic, and the panel also systematically reviewed reference lists and consulted with experts in this field.

When appropriate based on the available data, a series of meta-analyses, using both newly identified data and those contained in the 2001 report, allowed estimation of the pooled effect of treatment of bacterial vaginosis on preterm delivery (before 37, 34, or 32 weeks) and on low birthweight and preterm, premature rupture of membranes.

Based on this review and meta-analyses, the USPSTF panel concluded that current evidence is insufficient to evaluate the balance of benefits and harms of screening for bacterial vaginosis in pregnant women at high risk for preterm delivery (I statement).

The USPSTF panel issued the recommendation not to screen for bacterial vaginosis in pregnant women at low risk for preterm delivery (D level recommendation).

In asymptomatic pregnant women at low risk for preterm delivery, studies are lacking, and evidence is therefore poor, for harms of screening for bacterial vaginosis. However, evidence is fair that false-positive results from screening lead to harms caused by treatment.
In asymptomatic pregnant women at high risk for preterm delivery, studies are lacking, and evidence is therefore poor, for harms of screening for bacterial vaginosis. Studies on the harms of treatment have yielded conflicting results in this population.

The overall USPSTF assessment and conclusion is that for asymptomatic pregnant women at low risk for preterm delivery, there is moderate certainty that screening for bacterial vaginosis has no net benefit. For asymptomatic pregnant women at high risk for preterm delivery, the evidence is conflicting, preventing determination of the balance of benefits and harms.
"Available evidence on treatment benefit is conflicting," the USPSTF writes. "Additional research is needed to evaluate the benefit of screening and treating asymptomatic bacterial vaginosis in women at highest risk for preterm delivery."

Risk factors for preterm delivery include African American race, pelvic infection, and previous preterm delivery.

Gram stain or the Amsel clinical criteria can be used to diagnose bacterial vaginosis. Clinical diagnosis by the Amsel criteria requires that 3 or 4 of the following criteria be present: (1) vaginal pH of more than 4.7, (2) presence of clue cells on wet mount, (3) thin homogeneous discharge, and (4) amine "fishy odor" when potassium hydroxide is added to the discharge.
Although the optimal treatment regimen for bacterial vaginosis is unclear, oral or vaginal gel metronidazole and oral or vaginal cream clindamycin are typically used.

"Bacterial vaginosis is more common among African-American women, women of low socioeconomic status, and women who have previously delivered low-birthweight infants," the USPSTF concludes. "Research is also needed to assess which screening tests providers use to diagnose bacterial vaginosis in clinical practice and the accuracy of these tests. Finally, continued research is needed to determine the optimal treatment regimen for bacterial vaginosis."
The Oregon Evidence-based Practice Center under contract to the Agency for Healthcare Research and Quality, Rockville, Maryland, supported this study.
Ann Intern Med. 2008;148:214-219, 220-233.

Clinical Context
In women of childbearing age, bacterial vaginosis is the most frequently documented lower genital tract syndrome. There are well-documented associations between bacterial vaginosis and adverse pregnancy outcomes, including premature birth or low birthweight. Good-quality evidence indicates that screening tests can detect bacterial vaginosis.

Because it is easy to screen for and treat bacterial vaginosis, some experts have recommended screening all pregnant women for this condition. However, in this review, the USPSTF finds insufficient evidence to recommend either for or against screening for the syndrome in pregnant women at high risk for premature delivery.

Pearls for Practice
The USPSTF review suggests that there is good evidence that screening for bacterial vaginosis does not benefit pregnant women at low risk for premature delivery, and the expert USPSTF panel therefore recommends against screening low-risk women for bacterial vaginosis (D level recommendation).

Based on this review and meta-analyses, the USPSTF panel concluded that current evidence is insufficient to evaluate the balance of benefits and harms of screening for bacterial vaginosis in pregnant women at high risk for preterm delivery (I statement).

Source: Medscape