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Group B streptococcal infection in pregnant women

Karen M Puopolo, MD, PhD
Lawrence C Madoff, MD
Carol J Baker, MD
Section Editor
Daniel J Sexton, MD
Deputy Editor
Allyson Bloom, MD


Group B streptococcus (GBS; Streptococcus agalactiae) is a gram-positive coccus that frequently colonizes the human genital and gastrointestinal tracts, as well as the upper respiratory tract of young infants [1,2]. It is an important cause of illness in infants, pregnant women, and adults with underlying medical conditions [3].

In pregnant and postpartum women, GBS is a frequent cause of asymptomatic bacteriuria, urinary tract infection, upper genital tract infection (ie, intraamniotic infection or chorioamnionitis), postpartum endometritis (8 percent), pneumonia (2 percent), puerperal sepsis (2 percent), and bacteremia without a focus (31 percent). It also can cause focal infection such as meningitis and endocarditis, albeit rarely. The serotype distribution of invasive GBS infection in pregnant women is similar to that of early-onset neonatal disease [4].

GBS infection in pregnant women will be reviewed here. The microbiology of GBS; GBS infection in neonates, young infants, and nonpregnant adults; and prevention strategies through chemoprophylaxis and vaccination are discussed separately. (See "Group B streptococcus: Virulence factors and pathogenic mechanisms" and "Group B streptococcal infection in neonates and young infants" and "Group B streptococcal infections in nonpregnant adults" and "Neonatal group B streptococcal disease: Prevention" and "Management of the infant whose mother has received group B streptococcal chemoprophylaxis" and "Vaccines for the prevention of group B streptococcal disease".)


GBS infections in pregnant women include urinary tract infection, upper genital tract infection, intraamniotic infection, endometritis, and bacteremia [5,6]. Invasive maternal infection with GBS is associated with pregnancy loss and preterm delivery [4,7]. Prior to the widespread use of maternal intrapartum chemoprophylaxis, maternal colonization with GBS conferred an increased risk of chorioamnionitis, and early postpartum infection [8,9]. There does not appear to be an association between maternal GBS colonization during pregnancy and preterm delivery [10].

In the Centers for Disease Control and Prevention (CDC) surveillance study including data collected from 1999 to 2005, the rate of invasive infection (defined as isolation of GBS from a blood or other usually sterile body site, excluding urine) in pregnant women was 0.12 per 1000 live births (range 0.11 to 0.14 per 1000 births) [4]. Upper genital tract infection accounted for approximately one-half of cases, isolated bacteremia occurred in one-third of cases, and GBS was isolated from maternal blood in approximately one-half of cases. Among women for whom pregnancy outcome data were available, approximately one-half of the maternal GBS infections led to fetal death, neonatal infections, neonatal death, or pregnancy loss.

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Literature review current through: Nov 2017. | This topic last updated: Jul 15, 2017.
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