Group B Strep (cont.)

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What causes group B strep infection?

Group B strep can normally be found in about 25% of all healthy adult women. It can commonly be found in the intestine, vagina, and rectal area. Most women who are carriers of the bacteria (colonized) will not have any symptoms; however, under certain circumstances, infection of both the mother and/or the newborn can develop. In newborns, if the group B strep infection develops in the first week of life, it is termed early onset disease. If the group B strep infection develops from 1 week to 3 months of age, it is referred to as late-onset disease. Approximately 1,200 babies in the United States develop early onset disease each year, with similar rates for late-onset disease.

How is group B strep transmitted?

In newborns, GBS infection is acquired through direct contact with the bacteria while in the uterus or during delivery; thus, the infection is transmitted from the colonized mother to her newborn. Approximately 50% of colonized mothers will pass the bacteria to their babies during pregnancy and vaginal delivery. However, not all babies will be affected by the bacteria, and statistics show that about only one of every 100-200 babies born to a GBS-colonized mother will actually go on to develop GBS infection.

Group B strep infection is more common in African Americans than in whites. There are also maternal risk factors that increase the chance of transmitting group B strep to the newborn leading to early onset disease:

  • Labor or membrane rupture before 37 weeks gestation
  • Membrane rupture more than 18 hours before delivery
  • Urinary tract infection with GBS during pregnancy
  • Previous baby with GBS infection
  • Fever during labor
  • Positive culture for GBS colonization at 35-37 weeks

Late-onset GBS infection occurs more commonly in babies who are born prematurely (<37 weeks) and in those babies whose mother tested positive for GBS during pregnancy.

Group B strep infection is not a sexually transmitted disease (STD).

Medically Reviewed by a Doctor on 4/10/2015

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