Glossary

Term · Pregnancy: Your Body

group B streptococcus

Also: GBS, Streptococcus agalactiae

A common bacterium that lives in many adults without symptoms, and can pass to a baby during birth. Testing in late pregnancy looks for it.

In plain words

Group B streptococcus is a bacterium that lives in the gut and lower genital tract of many adults. Most people carry it without any symptoms. In late pregnancy, a swab can check for it. If a person carries it, the bacterium can reach the baby during labor or when the water breaks. Most babies who are exposed stay well. A small number develop serious infection in the first days of life, which is why the condition is part of newborn care. Clinicians may give for people who test positive or who have certain risk factors. Fever or poor feeding in a newborn is a reason for prompt evaluation.

The deeper version

Streptococcus agalactiae colonizes the gastrointestinal and lower genital tract in roughly 10 to 30 percent of pregnant women. Intrapartum transmission is the main route to early-onset neonatal disease, which presents in the first week of life. Screening at 36 to 37 weeks by vaginal-rectal culture, or a risk-based approach, is described in CDC guidance (Verani and colleagues, MMWR, 2010) and in ACOG Committee Opinion 797 (2020). Intrapartum antibiotic prophylaxis is standard for carriers. Decisions for people not screened depend on risk factors, including , rupture of membranes lasting 18 hours or more, and intrapartum fever. Early-onset disease declined substantially after screening and prophylaxis were introduced. The debate concerns universal versus risk-based screening, the logistics of intrapartum treatment, and antibiotic resistance.

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Sources

  • Verani JR, McGee L, Schrag SJ (CDC) — Prevention of perinatal group B streptococcal disease: revised guidelines from CDC, 2010. MMWR Recommendations and Reports, 2010
  • American College of Obstetricians and Gynecologists — Committee Opinion 797: Prevention of group B streptococcal early-onset disease in newborns (2020)

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