Epidemiology of group B streptococcal colonization in pregnancy.

These data support the conclusions that: 1) An intrapartum screening program for GBS colonization favorably affects the outcome of GBSD, with mortality decreased to 10%. 2) Four risk factors--ABO blood group B, unregistered status, PROM and premature labor at less than 32 weeks--identify 83% of mothers whose infants develop GBSD. 3) There is no association between internal monitoring and mode of delivery and the vertical transmission of GBS. 4) Duration of membrane rupture does not affect vertical transmission or development of early-onset disease. This differs from previous findings. 5) Lastly, our findings regarding the natural history of asymptomatic infant carriers suggest that these infants play a previously unsuspected role in the epidemiology of GBS in the entire population.