Group B Strep: A Threat to Newborns That Doesn't Have to Be
FRIDAY Sept. 7, 2007 -- One in four women carries the bacterium Group B streptococcus, the most common cause of life-threatening infections in newborns. Yet most women don't know it.
That same germ can wreak havoc on a newborn child, with infection during birth possibly leading to blindness, deafness, retardation, physical disability and, in the worst cases, death.
There's a simple test that can determine whether a pregnant woman carries GBS, and an effective antibiotic therapy for protecting her child during delivery. Yet, approximately one of every 100 to 200 babies whose mothers carry GBS will become infected and need treatment, according to the U.S. Centers for Disease Control and Prevention.
"It can kill and maim, and 90 percent of it is preventable," said Dr. James A. McGregor, visiting professor of clinical obstetrics and gynecology at the University of Southern California Keck School of Medicine in Los Angeles. "How often in life do you get the chance to prevent 90 percent of something awful?"
As a result, doctors are urging women to make sure they are tested for presence of the bacterium -- and that they make sure steps are taken during delivery to protect their baby.
With a swab of a woman's rectum and vagina, doctors can determine whether she carries GBS.
Both the U.S. Centers for Disease Control and Prevention and the Society of Obstetricians and Gynaecologists of Canada have guidelines that recommend that doctors screen every pregnant woman for GBS. The screening should take place between the 35th and 37th week of pregnancy. If a woman hasn't received a GBS screening by then, she should ask her doctor about it, according to the guidelines.
If a woman tests positive for GBS, she should be given intravenous antibiotics for at least four hours before she delivers, the guidelines say.
Doctors believe that babies who are infected take the bacterium into their bodies by ingesting GBS-containing amniotic or vaginal fluids during labor and delivery, according to the March of Dimes.
"We can't make a normal bacteria that's just living there go away by antibiotics," said Dr. Carol Baker, a professor of pediatrics, microbiology and immunology at the Baylor University College of Medicine, and head of the section for infectious diseases in the college's Department of Pediatrics. "But what we can do, if they are carrying the Group B strep, we give them antibiotic during labor.
"It fills the fluid around the baby, the amniotic fluid, with antibiotic," Baker said. "The baby is in an antibiotic bath, as it were." The antibiotic also floods the mother's blood and the birth canal.
"We can't make it [the germ] go completely away, but we can get the number really, really low -- enough so that the baby won't get a life-threatening infection," she said.
There's a one-in-100 chance that a GBS carrier's baby will become sick from infection with the bacterium. The risk rises to 4 percent under certain circumstances, including preterm delivery, prolonged rupture of the membranes, or fever during labor, according to the March of Dimes.
About 5 percent of babies infected with Group B strep die. Most who survive develop normally, but among those who develop meningitis as a result of GBS, up to 50 percent suffer lasting neurologic damage that can include cerebral palsy, sight and hearing loss, mental retardation, learning disabilities and seizures.
McGregor said that now that screening guidelines are in place, researchers want to eliminate the small number of infections that continue to occur. They are trying to figure out how to better improve the testing, making it quicker and more accurate. They're also looking at ways to make sure mothers get a sufficient dose of antibiotics, even if their labor appears to be a quick one, he said.
"Many hospitals used to have antibiotics on the ward that they could administer," McGregor said. "Now the request has to go to the pharmacy, and that can take an hour the mother might not have."
A potential vaccine that could be given to all women of childbearing years is another option.
"There's increasingly a clearly felt imperative to make a vaccine for Group B strep available for pregnant women," McGregor said.
There are a couple of candidate vaccines that have been identified, but research on them has ground to a halt, because no drug company is interested in pursuing them, he said. In effect, the Group B strep vaccine has become an "orphan" of medical science.
"We need to change our policies about 'orphan' vaccines and 'orphan' therapies," providing incentives and encouragement for research, McGregor said.
Finally, McGregor and Baker believe doctors need to better explain the GBS test at the time it is administered, so women with the bacterium understand that they need antibiotics and know to ask for them.
"If you say, 'I am group B strep positive, I need my antibiotics,' people will be responsive to you," Baker said. "We need to explain the test to the woman. Then she can really help advocate for the right thing being done in a timely fashion."
To learn more, visit Group B Strep International.
Posted: September 2007