Most studies demonstrate that untreated bacterial vaginosis increases the rate of preterm birth. Despite this, there is no evidence that screening and treatment of asymptomatic bacterial vaginosis nor interpregnancy treatment of endometritis decreases the subsequent rate of preterm birth. However, treatment of symptomatic bacterial vaginosis has been associated with a modest reduction in subsequent preterm birth. Potential mechanisms for this reduction include a decrease in peripheral maternal pro-inflammatory activation of the TH1 inflammatory cascade with treatment, however this direct pathway has not been elucidated. The approved treatment for bacterial vaginosis during pregnancy consists of Metronidazole 500mg BID for 7 days. A more complete understanding of the effect of Metronidazole on maternal inflammation would be useful in designing strategies to reduce the rates of preterm birth.