Context:  While an association between bacterial vaginosis and preterm labour has been established, the relative contribution of this condition remains controversial.
Objective:  To determine whether bacterial vaginosis is likely to be an important contributing factor in preterm births in Otago, New Zealand, a region with a historically high rate of such births.
Design and setting:  Women receiving antenatal care from Queen Mary Maternity Services were studied prospectively. Cases were women presenting with preterm labour or premature rupture of membranes. Controls had uncomplicated pregnancies and delivered at term.
Patients and methods:  Vaginal swabs from 44 cases and 72 controls were examined by amplification of bacterial 16S rRNA genes followed by denaturing gel gradient electrophoresis. Atopobium vaginae, a bacterial vaginosis‐associated bacterium, was detected in a separate polymerase chain reaction. Nugent Gram stain scoring of vaginal swabs from 44 cases and 69 controls was also carried out.
Results:  Denaturing gel gradient electrophoresis revealed three major types of band profiles corresponding to normal, intermediate and bacterial vaginosis microflorae. There were significantly more cases with bacterial vaginosis band profiles compared with controls (P = 0.024). More cases had intermediate or bacterial vaginosis Nugent scores compared with controls (P = 0.022). Conversely, controls were more likely to have normal scores than cases (P = 0.022). Atopobium vaginae was equally distributed between the cases and controls.
Conclusions:  Women in the Otago region undergoing preterm labour were approximately twice as likely to have a bacterial vaginosis type vaginal microflora as controls. In preterm labour, the incidence of bacterial vaginosis was comparable with that found elsewhere, suggesting that current guidelines for treatment and detection of this condition are appropriate.