Preterm labour involves multiple causes - one of the most significant factors being a prior history of preterm birth. Infection is another major cause of preterm labour (PTL) and is estimated to cause up to 30% of PTL. Bacterial Vaginosis (BV) is an alteration in the endogenous vaginal microflora preceded by a decreased presence of Lactobacilli species and increased growth of gardnerella and other pathogens. BV is a strong risk factor for PTL, and is associated with a 40% increased risk in some populations. Initial studies suggested that the treatment of BV with antibiotics could decrease the incidence of PTL, but this has not been confirmed by randomized trials. There is substantial evidence that the "normal" lactobacillus dominated urogenital microflora play an important role in maintenance of a healthy urinary and reproductive tract.