What is Group B Streptococcus (GBS)?

Group B Streptococcus (GBS) is a normal bacteria (germ) that is present in up to 10 to 30 percent of pregnant women. A woman with GBS can pass the bacteria to her infant during delivery. Most newborns who get GBS do not become ill. However, the bacteria can cause serious and even life-threatening infections in a small percentage of newborns.

How does a baby get GBS?

In pregnant women, GBS is found most frequently in the vagina and rectum. GBS is different than strep throat, which is Group A Streptococcus. GBS can live in a pregnant woman's body and cause symptoms and an infection. GBS can also live in a pregnant woman's body and not cause any symptoms and not pose any danger to her health. In this situation, the woman is called a "carrier."

Early infection: Of the babies who become infected, most of the infections (75 percent) occur in the first week of life. In fact, most infection is apparent within a few hours after birth. Sepsis, pneumonia, and meningitis are the most common problems. Premature babies face greater risk if they become infected, but most babies (75 percent) who get GBS are full-term.

Late infection: GBS infection might also occur in infants one week to several months after birth. Meningitis is more common with late-onset GBS-related infection than with early-onset infection. About half the babies who develop late-onset GBS got the infection passed to them from their mothers during birth. The source of the infection for others with late disease is thought to be contact with other people who are GBS carriers, or the GBS "carrier" mother after birth, or perhaps still other unknown sources. Late-onset infection is less common and is less likely to result in a baby's death than early-onset infection.

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