From a review of the literature it is concluded that one forth of preterm deliveries are associated with infections. The presence of Group B Streptococci (GBS), Ureaplasma urealyticum, Chlamydia specific IgM antibodies, and bacterial vaginosis may be of importance, but the odds-ratio is seldom more than two, and the studies do not include confounder control. Treatment with penicillin may be indicated in pregnant women (1) with GBS-uri (2) who have given birth to at child with neonatal GBS meningitis, or (3) with preterm labour and/or rupture of fetal membranes.