Abstract. The incidence of neonatal septicaemia associated with prolonged rupture of foetal membranes, discoloured amniotic fluid and/or maternal fever was investigated. A total of 807 blood cultures were performed on 329 neonates, the placental end of 239 umbilical cords and on 239 mothers. The study showed that in 97% of the neonates with a complicated delivery there was no evidence of septicaemia. Septicaemia was verified in 3% of the infants, and was intimately associated with low birth weight (p=0.02), neonatal asphyxia (p<10‐4), clinical evidence of septicaemia (p<10‐4) and maternal fever (p=0.002). The incidence was particularly high in premature infants with neonatal asphyxia (27%) and in neonates born to febrile mothers (20%). None of the mothers showed any evidence of septicaemia, and haematogenous, transplacental spread of infection to the child was not seen. Routine prophylactic antibiotic therapy in neonates with a complicated delivery should therefore be reserved, in our opinion, for those infants at high risk of infection.