Aetiological relationships between cerebral palsy, preterm birth, small-for-gestational-age (SGA) birth and selected feto-maternal factors were investigated in a case-control study of all moderate and severe cerebral palsy cases born in Western Australia between 1980 and 1986 (n = 215). Cases were individually matched to three controls of the same gender and plurality born in the same year. Two of the controls were matched to the index cases for gestational age, one of which was also matched for birthweight. Pre-eclampsia and urinary tract infections were not significantly associated with cerebral palsy. The significant association of antepartum haemorrhage with cerebral palsy was accounted for by its associations with preterm birth. Congenital malformations and non-cerebral palsy neurological disorder were significantly associated with cerebral palsy; these associations were only partially accounted for by adjusting for preterm birth and small-for-gestational-age birth. This study shows that some of the risk of cerebral palsy associated with the antenatal antecedents of some common feto-maternal factors is mediated through preterm birth, confirming the importance of interrelationships between antenatal antecedents in the aetiology of some cerebral palsy. Perinatal and post-neonatal causes now account for only around 20% of all cerebral palsy. Future reductions in cerebral palsy incidence may therefore depend on acquiring greater knowledge of inter-relationships between antenatal antecedents.