Group B Strep (GBS) in Pregnancy

Group B Streptococcus (GBS) is a common bacteria in the gut and genital tract. When GBS causes an infection, it can lead to severe illness, brain damage, and death in vulnerable populations (especially newborns and those with weak immune systems) (1).

During the delivery, newborns may contract GBS from their mothers. Because of the high risk associated with GBS in neonates, and because pregnant women with GBS are generally asymptomatic, standard of care dictates that expectant mothers be tested for GBS in the third trimester of pregnancy using a swab sample (2). Babies who are suspected to have exposure to group B strep are closely monitored and treated at the first signs of infection in order to prevent infection-related damage (1).

Group B Streptococcus, also known as group B strep or GBS, is a bacterium that is part of the normal flora of the gut and genital tract (1). GBS bacteria is found in about 25% of healthy women, and often shows no physical symptoms. However, pregnant women colonized with GBS can pass the bacteria on to their offspring during labor and delivery, which can lead to serious infection in newborns (3). When GBS infection is present in neonates and young infants and is treated improperly, it can lead to meningitis, brain damage, cerebral palsy, seizure disorders, developmental disabilities, and other serious complications (1).

In infants, the two main types of GBS infection are early-onset and late-onset, though a third type, known as late, late-onset, also occasionally occurs. The types of neonatal GBS are differentiated as follows (1):

• Early-onset: Early-onset GBS generally presents with symptoms within 24 hours of birth, but can begin anywhere within six days of birth.
• Late-onset: Late-onset GBS usually presents with symptoms between four and five weeks after birth.
• Late, late-onset: Also known as very-late-onset GBS or GBS beyond early infancy, late, late-onset GBS present with symptoms after three months of age.

GBS is a naturally occurring flora, so many healthy women carry GBS in their bodies. A woman can carry the infection for a short period of time, it may come and go, or she may always have it. In newborn babies, GBS infection can be acquired through direct contact with the bacteria while in the uterus. However, babies more frequently contract it during delivery from bacteria in the birth canal (2).

The main risk factor for neonatal GBS infection is maternal GBS colonization (1). If a mother tests positive for GBS, the risk of a baby contracting GBS infection increases. Additional maternal risk factors that increase the chance of transmitting GBS to the newborn include (1, 4):

• Delivery before 37 weeks gestation (premature birth)
• Premature rupture of the membranes (PROM)
• Chorioamnionitis
• Urinary tract infection with GBS during pregnancy
• Previous baby with GBS infection
• Fever during labor
• Positive culture for GBS colonization at 35 – 37 weeks

Women with GBS typically have no signs or symptoms of the infection.  However, GBS can occasionally cause burning, irritation, or unusual discharge which may be mistaken for a yeast infection.

Signs and symptoms of GBS infection in babies include the following (1, 4, 6):

• Presence of sepsis, pneumonia, or meningitis
• Fever or temperature instability
• Breathing problems/grunting sounds
• Apnea (periods without breathing)
• Cyanosis (bluish coloring of the skin)
• Seizures
• Limpness (hypotonia) or stiffness (hypertonia)
• Heart rate and blood pressure abnormalities
• Difficulty latching on to the mother’s breast or feeding
• Irritability and fussiness/unusually anxious behavior

Since women infected with GBS usually display no signs or symptoms of the infection, and since the potential danger to babies is severe, it is standard of care that all expectant mothers get tested for GBS during the third trimester of their pregnancy. The physician performs the test by taking a swab sample from the woman’s vagina and rectum. The swab is then sent to a lab for testing. If the test is positive for GBS, steps are taken to protect the baby from infection.

If the woman has already given birth and there is a suspicion that the baby has GBS, a sample of the baby’s blood or spinal fluid will be sent to a lab for evaluation.

GBS infection and disease are diagnosed when the bacteria are grown from cultures of the fluid samples. The cultures take several days to grow, so it may be two to three days before the results of the lab analysis are received (1, 2, 3).

When a woman tests positive for GBS, the physician must devise a plan to minimize the baby’s exposure to the infection during the birthing process. In order to prevent GBS in babies, antibiotics must be administered to the mother during labor. In fact, antibiotic treatment is recommended for (2):

• Women who delivered a previous infant with GBS infection
• Women with GBS bacteriuria (bacteria in the urine) in the current pregnancy
• Women with a GBS-positive screening result in the current pregnancy
• Women with unknown GBS status who deliver at less than 37 weeks’ gestation, have an intrapartum temperature of 38º C (100.4º F) or greater, or have rupture of membranes for 18 hours or longer.

Penicillin is the preferred medication for intrapartum antibiotic treatment, and ampicillin is an acceptable alternative (2).

Generally, the type of birth (C-section versus vaginal delivery) does not affect how a physician will proceed with regards to GBS prophylactic treatment. What is important is whether the baby is exposed to the bacteria, and how to best protect the baby from infection.

While maternal antibiotics and other preventative measures may reduce a baby’s chance of contracting GBS, all newborns born to mothers who are GBS carriers should be carefully monitored to identify the earliest manifestations of the disease. GBS in neonates is treated via a combination of antimicrobial therapy and supportive care (1).

Antimicrobial therapy

When the signs and symptoms are first noticed in an infant, but an official GBS diagnosis has not yet been made, doctors must administer what is known as “empiric” antibiotic therapy. Empiric antibiotic therapy includes broad coverage for bacteria and other organisms that can cause early- and late-onset disease in neonates. Once a definitive GBS diagnosis has been made, physicians must administer penicillin alone to fight GBS infection (1).

Supportive care

Alongside antimicrobial therapy, the following measures may be taken to help in the treatment of GBS (1):

• Management of seizures
• Treatment of anemia
• Ventilatory support
• Treatment of shock
• Fluid and electrolyte maintenance

When risk factors for GBS infection are present, it is essential that the physicians monitor the mother and baby very closely and follow guidelines and medical standards of care for treatment and prevention of GBS. It is negligence when a mother and baby are not properly tested for GBS, and when standards for treating the condition are not followed.