Study: Test All Pregnant Women for Group B Strep

Challenges policy of testing only at-risk moms for deadly germ

WEDNESDAY, July 24, 2002 (HealthDayNews) -- If all women were screened for a deadly bacteria they can pass on to their babies during delivery, the number of these infections would be reduced greatly.

A new study says widespread screening for Group B Streptococcus can cut the number of infections by more than half when compared to the current policy of testing only those mothers at risk of the germ. However, a second study warns against the overuse of antibiotics that would prevent the infection.

The findings run counter to guidelines from the government and medical groups on how to test for the pathogen. These groups give hospitals and doctors the choice of mass screening or risk-based testing for the microbe. It is the leading cause of infection deaths among babies in this country, sickening 1,600 and claiming 80 newborn lives each year.

Officials at the Centers for Disease Control and Prevention say they will be releasing new recommendations in the coming weeks that reflect the latest findings.

"Screening does prevent an important proportion of cases more than the risk-based approach," says Stephanie Schrag, an epidemiologist at the CDC who led the research. She adds the agency will now call exclusively for screening.

Women who test positive for the bacteria are given antibiotics during labor to prevent babies from acquiring the infection as they descend through the birth canal.

Roughly one in four pregnant women in this country carry Group B strep, which is typically harmless to adults but can cause serious illness in those with diabetes and other ailments.

For every 100,000 would-be mothers, risk-based testing would catch and prevent all but 70 cases of newborn infection, compared with just 30 under a mass screening plan, Schrag says. The death rate from the disease in babies is about 5 percent, she says, so screening could save potentially dozens more lives.

The study, reported in tomorrow's issue of The New England Journal of Medicine, compared screening with risk-based testing, in which doctors look for Group B strep in pregnant women whose odds of carrying the bug are high. These include women threatening early labor, those with a fever, and those whose amniotic sac ruptures at least 18 hours before delivery.

The researchers looked at nearly 630,000 live births between 1998 and 1999, and a narrower selection of 5,144 deliveries. Of those infants, 312 developed Group B strep within hours or days of being born. However, the risk of the disease was about 50 percent lower in the infants whose mothers were screened earlier in pregnancy than in the babies whose mothers had risk-based testing when they went into labor.

Schrag says 18 percent of women who received risk-based testing had strep that went unnoticed, accounting for the difference. These women would be identified by mass screening.

However, another new study, also appearing in the journal, waves a yellow flag at a policy that might lead to increased use of antibiotics during labor.

It found that blood infections from Group B strep among very lightweight newborns fell 70 percent during the 1990s, thanks to greater use of antibiotics to kill the germ. At the same time, however, the rate of Escherichia coli infections in these babies more than doubled, and 85 percent were resistant to the drugs prescribed to treat strep.

Schrag says the new CDC guidelines will raise the issue of drug resistance, and recommends watching for changes in rates of other germs that cause newborn blood infections.

However, she adds, her group's study found the share of women getting antibiotics won't change under a screening regimen, because many mothers who have risk-based assessment now get the drugs but don't need them.

"Under either strategy, the proportion of deliveries that will be getting antibiotics is the same," she says.

Dr. Carol Baker, a pediatrician at Baylor College of Medicine in Houston and a spokeswoman for the American Academy of Pediatrics, agrees a shift in strep testing policy is needed.

"It is dramatically obvious; there is no debate. These data are so solid that risk-based testing is not appropriate anymore," says Baker, referring to the CDC study.

Ideally, Baker and other experts believe the key to preventing strep B in newborns will be a vaccine. Researchers are now working on an inoculation against the bacteria, but none is yet available.

Baker, who is helping test a Group B strep vaccine, says the science behind it is "great," and the shot is safe and effective in the women who've used it. Yet, she laments that the pharmaceutical industry has shown no interest in developing the shot for pregnant women.

Eventually, Baker says, it will probably be available for adults, especially the sick and elderly. However, she's not optimistic drug makers will ever shed their fears of liability and start making the vaccine for a pediatric setting.

That means the public health community must continue to rely on antibiotics to control the germs. And while that tack has been working up to now, Baker says, "if we get antibiotic-resistant bacteria we're up the creek."

What To Do

For more on Group B strep, try the Centers for Disease Control and Prevention or the Group B Strep Association.

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