How is gbs (group b strep.) contracted?

Common hitch hiker: Group b strep is a common germ in nature & found at any one moment in the genital tract of ~1/3 of women.In most cases it is innocuous, causing no harm, although it sometimes can cause a uti. It can be there one week & gone the next however, if passed to a newborn during labor or delivery, a fraction will get very sick.I would consider any mom @ risk & rely on the ob's to monitor the situation.