The U.S. Centers for Disease Control GBS guidelines say this:
Heavy colonization, defined as culture of GBS from direct plating rather than only from select broth, is associated with higher risk for early onset disease. GBS identified in clean-catch urine specimens is considered a surrogate for heavy maternal colonization and also is associated with higher risk for early-onset GBS disease.
Unfortunately, this is not an area of my expertise but perhaps your midwife or doctor could interpret for you. If it is any help, the CDC guidelines also say that the attack rate for early onset GBS in the newborns of untreated GBS + women who do not have other risk factors (less than 37 wk pregnancy, membrane rupture longer than 12 hr, fever greater than 99.5 degrees) is 5 per 1000. The fatality rate for early onset disease in newborns is 4%, which would calculate to 2 per 10,000 in untreated GBS + women without the risk factors listed above.
I should add that I am not aware of any study that looked at the effect of vaginal exams or invasive procedures such as stripping membranes or internal fetal heart monitoring or contraction monitoring on GBS infections, although I have studies showing that uterine infection in general can be linked to number of vaginal exams and length of time. I would be willing to bet that one could show an equally marked reduction as with prophylactic antibiotics in GBS infection rates just by keeping instruments and fingers out of the vagina with none of the downsides of antibiotics. Those studies will never be done, though, because whatever else can be said against them, prophylactic antibiotics are effective at preventing early onset GBS. My sound bite on that issue is: "If they had had antibiotics in Semmelweis' time, doctors still wouldn't be washing their hands."
Thank you for your kind words about my book.
-- Henci |