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Am Fam Physician. 1998;57(11):2725

See related article on neonatal group B streptococcal infection.

What is group B strep?

Group B strep is a common name for a certain kind of streptococcal germ that lives on the skin of some women. Up to one third of pregnant women have these germs (also called bacteria). A woman who has group B strep living on her skin is “colonized” with this germ. For every 100 colonized women who have a baby, one or two babies are infected with these germs while they're being born. A woman who is colonized becomes “infected” when the group B strep germs get inside her body.

If I have group B strep, what could happen?

Group B strep can make you sick. Just as important, your baby could get the germs from you during delivery and also get sick. Infected babies need treatment. Of 10 infected babies, one or two get very sick. Your baby will be kept in the hospital some extra days for close watching (observation) if your doctor thinks the baby is infected with streptococci. Blood tests will be done to see if your baby has group B strep. If your baby has this germ, the doctor will give the baby antibiotics. Fortunately, most babies who are kept in the hospital for observation don't have group B strep.

How will I know I have group B strep? If I'm infected, what can I do?

Your doctor can take a skin culture to see if you have group B strep living on your skin. Then, when you're in labor, you can take antibiotics to kill those germs before your baby is born. If you take antibiotics while you're in labor, your baby probably won't get this infection.

Can antibiotic treatment cause any problems?

Yes. You might have an allergic reaction to the antibiotic. For example, about one of every 10 women who take penicillin gets an itchy rash. Dangerous reactions to penicillin don't happen very often, though. About one of every 10,000 women who take penicillin has a bad reaction and needs emergency treatment.

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