My midwife sent me the clinical practice guidelines for Ontario midwives regarding GBS. It takes a bit to wade through, but there's some good info there!

Here are a couple excerpts.

"The gastrointestinal tract acts as a reservoir for gbs and is most likely the source of vaginal colonization. Approximately 10% to 35% of pregnant
women are colonized with gbs in the vagina and/or rectum, with rates varying by study populations, specimen collection, or culturing techniques. (4)
A recent Canadian study determined the prevalence of gbs colonization in pregnant women at 36 weeks gestation to be 19.5%. (5)
When untreated, approximately 50% of infants born to gbs positive mothers become colonized and eogbsd (early onset GBS disease) develops
in 1% to 2% of these infants. (6)
This means that in a group of 1000 untreated women, approximately 195 will be gbs positive, 98 infants will become colonized, and 1-2 will develop
eogbsd."

"Early colonization and infection of a neonate is related to maternal vaginal colonization with gbs. Several other factors increase the risk of eogbsd. These include: preterm birth (< 37 weeks), low birth weight, prolonged rupture of membranes, intra-partum fever, chorioamnionitis and frequent (≥ 6) vaginal exams in labour."

"Summary of Prevalence, Incidence and Neonatal Complications associated with GBS:

10% to 35% of women are colonized with GBS
40% to 50% of babies born to colonized women are colonized when untreated (6)
1% to 2% of these colonized babies develop EOGBSD (6)
5% to 9% mortality rate in those babies who develop EOGBSD (10,11)

Using these statistics, if we take an initial group of
17 500 to 50 000 pregnant women:
5000 women will be GBS positive
2000 to 2500 babies will be colonized with GBS
20 to 50 babies will develop EOGBSD presenting as the following:
- bacteremia (64% to 83%)
- pneumonia (9% to 23%)
- meningitis (7% to 12.5%) (9,11)
1 to 4.5 babies will die due to EOGBSD (from the initial group of 17 500 to 50 000 pregnant women)

http://www.aom.on.ca/files/Health_Ca..._2012FINAL.pdf

There are two tables in the article which break down the risk factors and tell you what your risk is with each one, letting you know which are more "risky" risk factors, and which are less. They might be helpful to look at.

They also said that the chlorhexidine solution may be helpful in preventing infection in the baby, but a larger study is needed for definitive proof.