Preventing Early-Onset Disease
1. Testing Pregnant Women

CDC’s guidelines recommend that a pregnant woman be tested, or screened, for group B strep in her vagina and rectum when she is 35 to 37 weeks pregnant. The test is simple and does not hurt. A sterile swab (“Q-tip”) is used to collect a sample from the vagina and the rectum. This is sent to a laboratory for testing.

About 25% of pregnant women carry group B strep in the rectum or vagina. Those women are considered group B strep positive. A woman may test positive at certain times and not at others. That’s why it’s important for all pregnant women to be tested for group B strep between 35 to 37 weeks of every pregnancy.

A woman who has the bacteria in her body usually does not feel sick or have any symptoms. However, she is at higher risk for passing group B strep to her baby during birth. Women should talk to their doctor about their group B strep status.

2. Antibiotics During Labor

Footprint-colorful heartTo help protect their babies from infection, pregnant women who test positive for group B strep in the current pregnancy should receive antibiotics (medicine) through the vein (IV) during labor. Also, pregnant women who have group B strep detected in their urine during the current pregnancy or who had a previous infant with group B strep disease should receive antibiotics during labor; they do not need to be screened at 35-37 weeks because they should receive antibiotics regardless of the screening result. Pregnant women who do not know whether or not they are group B strep positive when labor starts should be given antibiotics if they have:

  • labor starting at less than 37 weeks (preterm labor);
  • prolonged membrane rupture (water breaking 18 or more hours before delivery); or
  • fever during labor.

Antibiotics help to kill some of the group B strep bacteria that are dangerous to the baby during birth. The antibiotics help during labor only — they can’t be taken before labor, because the bacteria can grow back quickly. Penicillin is the most common antibiotic that is given. For women who are severely allergic to penicillin, there are other antibiotics that can be given. Women should tell their doctor or nurse about any allergies during a checkup and try to make a plan for delivery. When women get to the hospital, they should remind their doctor if they are allergic to any medicines.

Penicillin is very safe and effective at preventing group B strep disease in newborns. There can be side effects from penicillin for the woman, including a mild reaction to penicillin (about a 10% chance). There is a rare chance (about 1 in 10,000) of the mother having a severe allergic reaction that requires emergency treatment.

Preventing Late-Onset Disease

Unfortunately, the method recommended to prevent early-onset disease (giving women who are group B strep positive antibiotics through the vein (IV) during labor) does not prevent late-onset disease. Although rates of early-onset disease have declined, rates of late-onset disease have remained fairly stable since 1990. At this time, a strategy has not yet been identified for preventing late-onset group B strep disease.

Alternative Prevention Strategies

There is no group B strep vaccine currently available to help mothers protect their newborns from group B strep disease. Researchers are working on developing a vaccine, which may become available one day in the future. Antibiotics taken by mouth instead of through the vein, and antibiotics taken before labor and delivery are not effective at preventing newborn group B strep disease. Birth canal washes with the disinfectant chlorhexidine do not reduce mother to baby transmission of group B strep bacteria or the risk of having a baby with early-onset disease. To date, receiving antibiotics through the vein during labor is the only proven strategy to protect a baby from early-onset group B strep disease.


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