Perinatal group B streptococcal colonization and infection.

Of 2,169 patients screened in labor for vaginal group B streptococcal colonization, 164 (7.6%) had positive results. Five hundred twenty-four of the patients were screened in the antenatal period, and 57 patients with positive tests for group B streptococcus were treated in labor with intravenous ampicillin. Four of the treatment group gave birth to colonized infants but none became infected. Of the 136 untreated mother-infant pairs with positive tests, 62 neonates were colonized, nine became infected, and three died. In the presence of an attack rate of 6.6% among infants born to colonized mothers, antenatal screening and treatment in labor of mothers colonized with group B streptococcus will reduce neonatal colonization and infection.