One hundred and sixty (160) women at high risk for PTL, based on a prior history of preterm birth, will be approached at their first antenatal visit to participate. Recruitment of 54 patients with symptomatic or asymptomatic BV (based on Nugent Scoring). Women with documented BV will be randomized to either treatment with lactobacilli preparation (n=27) or placebo (n=27). Women with symptomatic BV will be treated with oral Metronidazole prior to starting the lactobacilli or placebo. None of the subjects, researchers or clinical staff will know which preparation each woman receives.