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Group Beta Streptococcus (GBS)

Group Beta Streptococcus (GBS) is not the same bacteria that causes strep throat.  It is part of the normal bacteria that exist in the gut.

GBS bacteria is transient (meaning that it comes and goes) and fast growing

10-30% of women are colonized with GBS at any given time.  Colonization is not infection, and is usually asymptomatic in the mother.

Of babies born to colonized mothers not given antibiotics in labor, about 50% become colonized.  only 1% of colonized babies will develop infection.  Most babies who are colonized remain healthy, but infection in the newborn can have serious consequences.   


  • To screen for GBS the vagina and rectum are swabbed.  You may choose to do the swab yourself, or to have it done by your care provider.  The swab is then sent into the lab for results.


  • GBS screening should be done around the 35th week of your pregnancy, because test results within 5 weeks of your due date usually remain the same until the birth.


There are two kinds of infection that can occur in a newborn; early onset GBS infection, and late onset GBS infection.  Early onset infection is thought to begin before the baby is born when GBS bacteria travel through the amniotic fluid to the newborn.  This is very rare, but serious if not treated.  Symptoms can be apparent anywhere from birth through the first week, but usually appear within 48 hours.  Late onset GBS occurs after the first week and is usually from an outside source (hospital, relatives, etc.)  Hand washing is very important to prevent late onset GBS infection.   There is currently no recommended medical prevention for late onset GBS infection.  It is treatable with antibiotics.

For a great article on Group Beta Strep and Pregnancy

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