The necessity of both anorectal and vaginal cultures for group B streptococcus screening during pregnancy

BACKGROUND Group B streptococcus (GBS) sepsis affects approximately 2 of every 1000 newborns. In an effort to decrease the incidence of neonatal GBS infection, the Centers for Disease Control and Prevention have established guidelines for screening and treatment during pregnancy. One strategy includes obtaining both vaginal and anorectal GBS cultures, then treating patients whose cultures are positive. Many of our patients are reluctant to undergo anorectal cultures. We conducted a study to determine whether performing cultures of both the vagina and anorectum would change patient management. METHODS We obtained vaginal and anorectal GBS cultures from 222 consecutive patients at 35 to 37 weeks' gestation. RESULTS Fifty-four patients (24.3%) had positive GBS cultures. Of those women, 10 (18.5%) had negative vaginal but positive rectal cultures. Thus, nearly one fifth of the patients with GBS colonization would not have received intrapartum antibiotics if only vaginal cultures had been performed. CONCLUSIONS Health care providers caring for pregnant patients should consider obtaining both vaginal and anorectal cultures when screening fur Group B streptococcus.