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More About Group B Strep

Frequently Asked Questions


Updated June 09, 2014

What are the risks of taking antibiotics to prevent group B strep disease in my newborn?

Penicillin is the most common antibiotic that is given. If you are allergic to penicillin, there are other antibiotics that can be given. 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.

However, a pregnant woman who is a group B strep carrier (tested positive) at full-term delivery who gets antibiotics can feel confident knowing that she has only a 1 in 4000 chance of delivering a baby with group B strep disease. If a pregnant woman who is a group B strep carrier does not get antibiotics at the time of delivery, her baby has a 1 in 200 chance of developing group B strep disease. This means that those infants whose mothers are group B strep carriers and do not get antibiotics have over 20 times the risk of developing disease than those who do receive treatment.

Can group B strep cause stillbirth, pre-term delivery, or miscarriage?

There are many different factors that lead to stillbirth, pre-term delivery, or miscarriage. Most of the time, the cause is not known. Group B strep can cause some stillbirths, and pre-term babies are at greater risk of group B strep infections. However, the relationship between group B strep and premature babies is not always clear.

Do people who are group B strep carriers feel sick?

Many people carry group B strep in their bodies, but they do not become sick or have any symptoms. Adults can have group B strep in the bowel, vagina, bladder, or throat. About 25% of pregnant women carry group B strep in the rectum or vagina. A person who is a ‘carrier’ has the bacteria in her body but may not feel sick. However, her baby may come into contact with group B strep during birth. Group B strep bacteria may come and go in people’s bodies without symptoms. A person does not have to be a carrier all of her life.

How does someone get group B strep?

The bacteria that cause group B strep disease normally live in the intestine, vagina, or rectal areas.

Group B strep colonization is not a sexually transmitted disease (STD). Approximately 25% (1 in 4) of pregnant women carry group B strep bacteria in their vagina or rectum. For most women there are no symptoms of carrying group B strep bacteria.

Will group B strep go away with antibiotics?

Antibiotics that are given when labor starts help to greatly reduce the number of group B strep bacteria present during labor. This reduces the chances of the newborn becoming exposed and infected.

However, for women who are group B strep carriers, antibiotics before labor starts are not a good way to get rid of group B strep bacteria. Since they naturally live in the gastrointestinal tract (guts), the bacteria can come back after antibiotics. 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 carriage between 35 to 37 weeks of every pregnancy. Talk to your doctor or nurse about the best way to prevent group B strep disease, or review the revised group B strep guidelines to learn more.

Is there a vaccine for group B strep?

There is not a vaccine right now to prevent group B strep. The federal government is supporting research on a vaccine for the prevention of group B strep disease.

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