Ask an Expert: Group B strep

Q. What is “Group B strep,” and how do I know if my unborn baby is at risk?

Answer from Dr. John V. McDonald, director of Neonatal Services at Providence St. Vincent Medical Center:

Group B Streptococcus (GBS) is a type of bacteria that is found in the lower intestine of 10 percent to 35 percent of all healthy adults and in the vagina and/or lower intestine of 10 percent to 35 percent of all healthy, adult women. GBS bacteria are a normal part of the bacteria commonly found in the human body, and usually do not cause problems.

However, in certain circumstances, GBS can cause serious bloodstream, respiratory, and other infections. About half of all GBS disease occurs in newborns who come into contact with their mother’s GBS bacteria after her water breaks or during childbirth. Group B Strep disease is the most common cause of newborn infections – about 8,000 babies contract a GBS infection each year. Group B Strep disease can cause permanent disability and even death.

Since the mid-1990’s, Providence Health & Services has been involved in supporting the implementation of protocols to reduce the incidence of GBS. To prevent infants from acquiring GBS disease, physicians are currently administering a penicillin shot or other antibiotics to high-risk pregnant women before they deliver. Women are defined as high-risk if they have one or more of the following risk factors:

  • They have had a positive GBS culture at 35 to 37 weeks gestation
  • They have had GBS bacteria in their urine during their current pregnancy
  • They have previously delivered an infant with a GBS infection

All of these factors are strongly associated with the baby getting infected.

The campaign to reduce the risk by administering antibiotics to high-risk mothers has been very effective. In 1995, 1.7 of every 1,000 babies born in Providence Health & Services had a GBS infection in the blood. In 2000, the rate was down to 0.1 babies per 1,000 born.

June 2003

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