Placental tissue and cord blood from women with preterm and term labour were examined for microorganisms and compared in this randomized prospective study. Of 100 women who delivered during a 12-month period, 50 had preterm labour and 50 had term labour. Samples were taken under sterile conditions for routine culture of anaerobic and aerobic bacteria immediately after delivery of the placenta. Fetal blood cultures were positive for 30% of the preterm group and 18% of the term group, which was statistically significant. Placental tissue cultures were positive for 58% of the preterm group and 28% of the term group. These data support previous reports that infection plays a significant role in preterm labour.