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Pregnancy test spotlight: Group B streptococcus

Here's a must for all moms-to-be late in pregnancy—get screened for group B streptococcus (GBS). It's a leading cause of life-threatening infections in newborns. But a simple, painless test can help protect your baby.

What is GBS?

GBS is very common type of bacteria. It can come and go naturally in your body. In women, it usually lives in the vagina and rectum. About one in four women carry it.

But GBS usually doesn't cause symptoms in adults. So most women who carry the bacteria don't know it. If you're pregnant, you can pass GBS on to your baby during labor. But while it may not be serious for you, it can be dangerous for your baby.

What are the risks for baby?

The good news: In most cases, GBS won't make a baby sick when mothers are treated with antibiotics during labor. The risk of passing GBS on to a baby is much higher when it is untreated. If it does infect newborns, it can cause pneumonia, meningitis or blood infections. 

Early GBS infections occur within a week of birth. They usually happen within the first 12 to 48 hours.

Late GBS infections occur after the first week of life. A late infection can come either from you or from other sources, such as people who carry the bacteria.

Some GBS infections have lasting effects. Those who have meningitis caused by GBS may develop cerebral palsy, seizures, hearing loss or learning disabilities.

About 5% of babies who get sick from GBS don't survive, even with treatment, according to the March of Dimes.

How to guard against it

The American College of Obstetricians and Gynecologists advises getting tested for GBS between 36 and 38 weeks of pregnancy. The test is an easy swab of the vagina and rectum—it won't hurt and it has no risks.

If you test positive for GBS, you'll need to have an antibiotic given to you through intravenous therapy (IV) during labor. This can help keep the bacteria from spreading from you to your baby during childbirth.

Women who have already had a baby with a GBS infection will also need antibiotics during labor. As will women who are at high risk for passing on GBS—for example, those who had a urine test that revealed GBS.

Antibiotics are also necessary if your GBS status isn't known and:

  • You have premature labor (before the 37th week of pregnancy).
  • Your water breaks 18 hours or more before delivery.
  • You have a fever during labor.

More pregnancy news

As your due date gets closer, you may be mentally preparing yourself for labor and delivery. One thing that can help is to decide on what kind of pain relief you want to use. There are more ways to manage it than you might suspect. Check out all your choices with this guide.

Additional sources: American Academy of Family Physicians; Centers for Disease Control and Prevention

Reviewed 1/25/2024

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