Group B Strep Infection

  • Medical Author:
    Steven Doerr, MD

    Steven Doerr, MD, is a U.S. board-certified Emergency Medicine Physician. Dr. Doerr received his undergraduate degree in Spanish from the University of Colorado at Boulder. He graduated with his Medical Degree from the University Of Colorado Health Sciences Center in Denver, Colorado in 1998 and completed his residency training in Emergency Medicine from Denver Health Medical Center in Denver, Colorado in 2002, where he also served as Chief Resident.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

What causes group B strep infection?

Group B strep can normally be found in about 25% of all healthy adult and pregnant 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 GBS infection develops in the first week of life, it is termed early-onset disease. If the GBS infection develops from 1 week to 3 months of age, it is referred to as late-onset disease. On average, approximately 1,000 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 GBS 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 4/29/2016

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