Despite substantial evidence linking BV with PTB, the results of trials of antibiotic treatment of BV in pregnancy have not produced clear evidence of benefit. The reason for this might be that it is not the eradication of unhealthy bacteria that is required but rather the replacement of unhealthy bacteria with the normally dominant lactobacilli. One way of achieving this could be by administering lactobacilli-containing capsules (probiotics) to pregnant women. Oral probiotics taken during pregnancy may directly alter the vaginal bacteria and in so doing protect the cervical opening from ascending infection.