Group B streptococcus and pregnancy

Group B streptococcus (GBS) is a bacterium that can cause serious infections. (Group A streptococcus is a different bacterium that causes the common strep throat.) For newborns, GBS can cause pneumonia, blood infections, bacterial meningitis (inflammation of the membranes surrounding the brain or spinal cord), and bone or joint infections.


Transmission/associated factors
Many people carry the GBS bacterium temporarily in their intestines, vagina, bladder or throat without being ill. It can cause illness in elderly adults or adults who have a chronic illness, pregnant women and newborns. GBS can be transmitted from mother to baby shortly before or during birth. Other modes of transmission are uncertain. GBS is not considered to be a sexually transmitted disease.
At the time of delivery, up to 30 percent of all mothers have GBS in their vaginas or intestines. About one of every 2,500 babies born in the United States become infected. In fact, group B streptococcus is the most common cause of life-threatening infections in newborns. The presence of GBS before delivery has been associated with premature delivery and premature rupture of the membranes (when your water breaks early).

Without preventive measures, about one of every 200 babies born to women with GBS in the vagina or rectum become infected. The risk of infection is highest for babies whose mothers have:

a previous baby who developed GBS disease
a urinary tract infection caused by GBS
a fever of 100.4°F or higher during labor
preterm labor or rupture of the membranes (before 37 weeks of pregnancy)
rupture of the membranes 18 hours or more before delivery
Early-onset vs. late-onset GBS disease
About 80 percent of infants who contract GBS do so in the first week of life, usually within the first six to 12 hours after birth. Typically acquired from the mother just before or during birth, this is considered early-onset GBS disease. Even with proper treatment, about 25 percent of newborns with early-onset GBS disease do not survive.

Late-onset GBS disease develops one week to several months after birth, with most cases occurring within the first three months. Late-onset GBS disease can be acquired from the mother during delivery or later through other sources, such as poor hand washing by those caring for the infant. The survival rate for late-onset GBS disease is significantly higher than the survival rate for early-onset GBS disease.


Signs/symptoms
For newborns, symptoms of early-onset GBS disease may include:
difficulty regulating temperature
fever of 100.4°F or more, taken rectally
grunting sounds
breathing difficulty
stiffness or limpness
Symptoms of late-onset GBS disease may include:

fever of 100.4°F or higher, taken rectally
stiffness or limpness
decreased appetite
inconsolable crying
Pregnant women who have group B streptococcus in their vaginas or rectums typically have no symptoms and develop no complications. However, some may develop uterine, urinary or C-section incision infections.


Diagnosis
If you or your baby develop any symptoms of GBS disease, consult a doctor immediately. Blood tests, cultures and X-rays may be done to diagnose the problem.

Treatment
If a GBS infection is suspected in a baby, antibiotic treatment begins at once -- even before test results are available. Mothers diagnosed with GBS infections are also given antibiotics. For both mothers and babies, penicillin and ampicillin are the antibiotics of choice. Others, such as clindamycin or erythromycin, may be used if allergies exist.

Complications
About 10 percent of infected babies don't survive, and others have permanent disabilities, such as hearing or vision loss, learning disabilities and mental deficiencies. For pregnant women and new mothers, GBS can cause infections in the uterus, urinary tract and C-section incision. The risk of preterm labor and premature rupture of the membranes is also higher.

Prevention
In 1996, two approaches for identifying high-risk mothers were recommended to prevent GBS disease in infants. Doctors could either screen for the bacteria during pregnancy or give antibiotics to women in labor with certain risk factors for GBS. Recent research, however, has shown the first approach to be most effective. The Centers for Disease Control and Prevention (CDC) now recommends screening all pregnant women for GBS.
For GBS screening, tissue samples are swabbed from the mother's vagina and rectum between 35 and 37 weeks of pregnancy. (Because GBS bacteria can come and go, cultures done earlier in the pregnancy are not as accurate.) Test results are available in 24 to 48 hours. A new test recently approved by the U.S. Food and Drug Administration provides results in one hour. The quick results allow women who go into labor before being tested or women who haven't had prenatal care to be treated if necessary. A positive result indicates GBS bacteria are present, but not that mother or baby are ill. If you test positive, you will then be given penicillin or another antibiotic, such as ampicillin, clindamycin or erythromycin during labor. Giving the medication earlier may not be effective because you may become infected again before the baby is born.

Antibiotics are also recommended if you've had a urinary tract infection caused by GBS during this pregnancy or a previous baby who developed GBS disease. Prior screening isn't necessary in these high-risk situations.

If the one-hour testing isn't available at your facility and you go into labor before GBS screening is done or the results are unknown, antibiotics are given if you have:

rupture of the membranes 18 hours or more before delivery
preterm labor or rupture of membranes (before 37 weeks of pregnancy)
fever of 100.4°F or higher during labor
A mother who receives antibiotics during labor has a one in 4,000 chance of delivering a baby with GBS disease -- significantly lower than the one in 200 chance without antibiotics. Infants born to mothers who receive the antibiotics should be observed in the hospital for any symptoms of GBS infection for at least 48 hours after birth. Discharge after 24 hours of observation may be considered if the mother received at least four hours of antibiotic therapy before delivery and the infant appears healthy and was born at 38 weeks of pregnancy or later. If an infant is born before 35 weeks of pregnancy, a blood test and culture may be done to determine if GBS is present.

On the research front
A vaccine to prevent GBS disease is currently being developed. The vaccine will stimulate the mother's body to produce antibodies that fight the GBS bacteria. Through the placenta, the infant would receive these antibodies and develop immunity to the bacteria.