Group B Streptococcal Infection
Group B streptococci frequently colonize the lower female genital tract, with an asymptomatic carriage rate in pregnancy of 5-30%. This rate depends on maternal age, gravidity, and geographic variation. Vaginal carriage is asymptomatic and intermittent, with spontaneous clearing in approximately 30% and recolonization in about 10% of women. Adverse perinatal outcomes associated with group B streptococcal colonization include urinary tract infection, intrauterine infection, premature rupture of membranes, preterm delivery, and postpartum endometritis.
Women with postpartum endometritis due to infection with group B streptococci, especially after cesarean section, develop fever, tachycardia, and abdominal distention, usually within 24 hours after delivery. Approximately 35% of these women are bacteremic.
Group B streptococcal infection is a common cause of neonatal sepsis. Transmission rates are high, yet the rate of neonatal sepsis is surprisingly low at less than 4:1000 live births. Unfortunately, the mortality rate associated with early-onset disease can be as high as 50% in premature infants and approaches 25% even in those at term. Moreover, these infections can contribute markedly to chronic morbidity, including mental retardation and neurologic disabilities. Late-onset disease develops through contact with hospital nursery personnel. Up to 45% of these health care workers can carry the bacteria on their skin and transmit the infection to newborns.
CDC recommendations for screening for and prophylaxis of group B streptococcal colonization are set forth in this chapter in the section on tests and procedures.
Brozanski BS et al: Effect of a screening-based prevention policy on prevalence of early-onset group B streptococcal sepsis. Obstet Gynecol 2000;95:496.
Shrag SJ et al: A population-based comparison of strategies to prevent early-onset group B streptococcal disease in neonates. N Engl J Med 2002;347:233.
Revision date: July 3, 2011
Last revised: by David A. Scott, M.D.