| Group B Strep Infection
Doctors are making progress in preventing GBS infection in newborns. In 1996, both the federal Centers for Disease Control and Prevention (CDC) and the American College of Obstetricians and Gynecologists (ACOG) issued guidelines to help health care providers identify and treat pregnant women who are at risk of transmitting GBS to their babies. The steps they recommend usually can prevent the infection in newborns of treated women.
How does a pregnant woman get GBS?
How does a baby acquire GBS infection?
About 80 percent of all GBS infections in newborns are early onset. Early onset infections are transmitted from mother to baby around the time of delivery. Late onset infections can be contracted at delivery or acquired after birth from other sources (such as from inadequate hand washing).
If a pregnant woman carries the GBS bacterium in her vagina or rectum at the time of labor and delivery, there is a 1 in 200 chance that her baby will become sick from GBS infection. The risk rises to 4 percent if a pregnant woman carries the bacterium and develops certain risk factors. These risk factors include: preterm (before 37 weeks gestation) labor, premature rupture of the membranes, prolonged rupture of the membranes (longer than 18 hours without delivering the baby), or fever (100.4°F or higher) during labor. Thirty to 70 percent of the babies of women who carry GBS in the vagina or rectum are born with the bacterium on their skin but most of these babies have no illness.
What types of symptoms does GBS infection produce in the newborn?
In spite of treatment with antibiotics, about 6 percent of babies with GBS die. Of the babies who live, about 90 percent have normal development without long-term effects. Fifteen to 30 percent of GBS-infected babies who develop meningitis suffer lastly neurologic damage in the form of cerebral palsy, sight and hearing loss, and/or mental retardation.
How can GBS infection of the newborn be prevented?
Penicillin, or a related drug called ampicillin, usually is used (clindamycin or erythromycin can be substituted in women who are allergic to penicillin). All of these antibiotics are considered safe for mother and baby, though there is some concern about allergic reactions. Studies to date suggest that 1 to 10 percent of women treated with penicillin will have a mild allergic reaction (usually a rash), and 1 in 10,000 will have a serious allergic reactions (anaphylactic shock), which requires prompt treatment and, in rare instances, can be fatal.
The first approach involves taking a swab of the vagina and rectum at 35 to 37 weeks of pregnancy. This sample is sent to a laboratory for a culture to test for the presence of GBS. Test results are available in 24 to 48 hours. If a pregnant woman is found to carry GBS, she will be treated with intravenous antibiotics during labor and delivery. Taking oral antibiotics prior to labor is not recommended, as they are not effective in preventing GBS infection in the newborn. (Some studies found that 20 to 70 percent of women treated with oral antibiotics during the third trimester still carried the bacterium at labor and delivery).
If a pregnant woman develops preterm labor before her culture test results are available, or before her provider has taken a culture, antibiotic treatment during labor and delivery is recommended. If a pregnant woman develops premature rupture of the membranes at less than 37 weeks gestation, her doctor will test her for GBS. If labor begins before test results are available (24 to 48 hours), intravenous antibiotics are recommended. However, if the pregnant woman does not go into labor right away, her doctor may either begin intravenous antibiotic treatment, then stop it if results come back negative, or may delay antibiotic treatment until either the results come back positive or she goes into labor (both approaches are considered effective).
The CDC and ACOG believe that doing the culture test at 35 to 37 weeks gestation is more accurate in detecting women who carry GBS at delivery. Because the GBS bacterium can come and go, testing earlier fails to identify the 7 percent of women who test negative at this time, but carry the bacterium at birth. Nearly all women who carry GBS at 35 to 37 weeks gestation will still carry the bacterium at delivery.
The second approach involves treating women who develop risk factors that increase the likelihood of passing GBS (if they carry it) to their babies. Providers who recommend this approach treat pregnant women with intravenous antibiotics in labor and delivery only if the following high-risk situations occur:
Both approaches recommend that all women who have previously delivered a baby with GBS infection or have a positive culture in the past be treated with intravenous antibiotics in labor and delivery. Antibiotic treatment during labor and delivery also is recommended for all women who have had a urinary-tract infection caused by GBS during pregnancy.
All pregnant women should discuss with their health care provider his or her approach to preventing GBS infection in the newborn. Both of the approaches discussed above will help prevent newborn GBS. More studies are needed to determine whether one of these approaches is more effective.
Can GBS cause complications in the mother, unrelated to newborn infection?
A urinary-tract infection also may result from GBS and should be treated during pregnancy with oral antibiotics. Symptoms of a urinary tract infection include fever, pain and burning during urination. Women with a urinary tract infection caused by GBS also should be treated with intravenous antibiotics during labor and delivery, since they are likely to have high levels of the bacterium in their bodies.
What research is being conducted on preventing GBS infections in newborns?