Why do we check for Group B Strep colonization

About 20 % of women normally carry Group B streptococcus as part of their nomral flora.  We culture all our pregnant women at about 35--6 wks along to determine who is a carrier.  We then treat them with antibiotics in labor not to eradicate but to reduce the amount of replicating bacteria in the birth canal so that when the baby is born, it is minimally exposed.  Most full term babies would do fine regardless of treatment, but a small number of untreated babies are vulnerable to an infection caused by GBS, so the American Academy of Pediatrics prefers we treat all colonized women in order to minimize that risk.  The most serious potential consequence of untreated GBS in the newborn is bacterial meningitis, and if a GBS+ patient is not adequately treated in labor (less than 4 hours from administration of the first antibiotics to delivery), the pediatrician may need to do bloodwork on the baby to insure it is well enough to go home from the hospital without antibiotics.  Even if you've been cultured positive in a prior pregnancy, we will still culture you again with each baby, as colonization can wax and wane over the years.  If you happen to test positive for GBS in the urine earlier in pregnancy, we will not re-culture at 35--6 weeks but rather treat you as a GBS+ patient.

For more information go to:
http://www.acog.org/~/media/For%20Patients/faq105.pdf?dmc=1&ts=20120821T1112475461