What is the role of GBS screening in the workup of chorioamnionitis?

Updated: May 08, 2018
  • Author: Fayez M Bany-Mohammed, MD; Chief Editor: Ted Rosenkrantz, MD  more...
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Antenatal screening uses rectovaginal specimens to detect the presence of maternal group B streptococcal (GBS) colonization at 35-37 weeks' gestation. Using these specimens, the Centers for Disease Control and Prevention (CDC) recommends selective growth of GBS in broth followed by cultivation using the plate method. [170, 171]  This is the criterion standard assay.​

The CDC does not recommend direct PCR detection of GBS in rectovaginal samples. Rather, a rectovaginal sample should undergo enhanced growth in selective broth before performing PCR. [170, 171] Maternal colonization with rectovaginal GBS increases the risk of chorioamnionitis, and intrapartum prophylaxis with antibiotics reduces the incidence of neonatal infection from GBS. [172, 173]

Missed screening and the failure to give intrapartum antibiotics is responsible for the persistence of neonatal GBS infection. [174] Therefore, for mothers that missed GBS screening at 35-37 weeks' gestation, intrapartum testing for GBS using rapid detection methods on vaginal secretions is an option recommended by some authorities. Intrapartum real-time PCR, performed on vaginal swabs, have been shown to be accurate by several investigators, and it performs as well or better than the antepartum culture for identification of GBS vaginal carriers during labor. [175, 176, 177]

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