USPSTF Recommends Against Bacterial Vaginosis Screening for Most Pregnant Women

By Will Boggs MD

April 09, 2020

NEW YORK (Reuters Health) - Based on updated evidence, the US Preventive Services Task Force (USPSTF) has reiterated its 2008 recommendation against screening for asymptomatic bacterial vaginosis in pregnant women who are not at increased risk for preterm delivery.

"The Task Force continues to recommend against screening for bacterial vaginosis (BV) in pregnant people who are not at increased risk for delivering their babies early because it does not help prevent preterm delivery," USPSTF member Dr. Melissa Simon from Northwestern University Feinberg School of Medicine, Chicago, told Reuters Health by email. "For women who are at increased risk for BV, it is unclear whether screening for BV can help prevent preterm delivery, and as such, the Task Force is calling for more research to help these women stay healthy."

Dr. Simon and colleagues on the Task Force base their updated recommendations on an evidence report prepared by Dr. Leila C. Kahwati from RTI International-University of North Carolina at Chapel Hill.

Most of the studies included in the evidence report (25/44) evaluated the accuracy of screening tests and found a broad range of accuracy, with sensitivities ranging from 36% to 100% and specificity ranging from 49% to 100%.

"We were surprised to find so little research on the accuracy of screening tests in pregnant women," Dr. Kahwati told Reuters Health by email. "Of the 25 studies we identified that evaluated the accuracy of screening tests for identifying bacterial vaginosis, only two were conducted among pregnant women. Further, most studies of test accuracy were not exclusively focused on asymptomatic persons."

In trials of general obstetric populations, there was no significant association between treatment of BV and spontaneous delivery before 37 weeks or any delivery before 37 weeks.

Five trials of women with a prior preterm delivery yielded inconsistent results, with three showing a significant beneficial effect of BV treatment and two showing no significant effect.

"It was surprising that only five studies have evaluated this subgroup," Dr. Kahwati said. "We looked at many factors that might explain the inconsistency in findings (study population, interventions, etc.), but there was no clear-cut explanation for the inconsistent findings."

Maternal adverse events associated with treatment appeared to be infrequent and minor, but there was inconclusive evidence about harms to the fetus from in utero exposure to metronidazole (used to treat BV).

"Additional research would be most valuable for clarifying the effectiveness of treatment among pregnant women with a prior history of preterm delivery, as that is where the current studies are inconsistent," Dr. Kahwati said. "Our study was focused on reviewing the evidence for screening and treatment among asymptomatic pregnant women; the findings are not generalizable to women who present with symptoms of bacterial vaginosis, for example, vaginal discharge or bad odor."

"While the Task Force recommends against screening in people without signs or symptoms who are not at increased risk, we encourage clinicians to talk with their patients about their risk factors and any concerns they may have," Dr. Simon said. "Until there is more evidence available on screening for BV in pregnant people at increased risk for preterm delivery, clinicians can continue to promote healthy pregnancies by using their best judgment based on patients' individual circumstances."

Dr. Louise C. Laurent from University of California, San Diego and Sanford Consortium for Regenerative Medicine, La Jolla, California and Dr. Amanda L. Lewis from Washington University School of Medicine in St. Louis, Missouri, who wrote an editorial related to this report, told Reuters Health by email, "We think it is likely that future studies leading to a deeper understanding of the vaginal microbiota will improve our chances of treating BV successfully. For example, there is growing evidence that certain 'favorable' vaginal bacterial species are associated with normal pregnancy outcomes, while other 'deleterious' vaginal microbes are associated with complications such as preterm birth."

"If therapies developed to convert a deleterious vaginal microbiome to a favorable one are shown to result in clinical benefit, for example, by combining antibiotic and probiotic treatments, then it may be reasonable to screen asymptomatic pregnant to identify those with deleterious vaginal microbes," they said. "We hope that other new strategies, such as timing of treatments or more personalized treatment protocols depending on what specific organisms are present, could prove more fruitful in the future."

Dr. Janneke van de Wijgert from University Medical Center Utrecht in The Netherlands and University of Liverpool in the UK, who has researched various aspects of BV, told Reuters Health by email, "Most of us believe that micro-organisms in the genital tract can cause preterm birth by causing inflammation. Many different conditions in the genital tract can cause inflammation, including vaginal yeast infections, bacterial vaginosis, sexually transmitted infections, such as chlamydia, and pathobionts, such as streptococci."

"In my opinion, interventions in pregnancy should not be directed to a single condition but should aim to achieve a healthy genital tract, free of all inflammatory conditions," she said.

"Pregnant women are screened for some conditions, but not all, so be vigilant," Dr. van de Wijgert said. "Check your patient's risk of sexually transmitted infections. If your patient has been diagnosed with BV regularly in the recent past, consider screening her regularly during her pregnancy."

The complete recommendation statement and the evidence report underlying it appear in JAMA.

SOURCE: JAMA, April 7, 2020.