The effects of multiple pre- and perinatal risk factors on the occurrence of cerebral palsy. A Norwegian register based study

AimsTo examine the effects of multiple risk factors on cerebral palsy (CP).Materials/methodsFor 176,591 Norwegian infants born 1996–98 and surviving the early neonatal period, data on a number of potential pre- and perinatal risk factors (RFs) for CP were available in the Medical Birth Registry of Norway. For 241 children with CP detailed clinical data were available in the Norwegian CP registry.ResultsIn children born at term, 31% had no RF, and none had five or more, while in children born preterm, 9% had no RF in addition to prematurity (p < 0.001 vs. term), and 5% had five or more (p < 0.02 vs. term). In both groups, few children shared the same combination of RFs. Interdependent sequences were more often observed among children born preterm than at term (p < 0.001 vs. term). The most detrimental effect was observed for the combination of maternal disease and low 5-min Apgar score, registered in 11.2% of children with CP. The combination of maternal disease and premature birth had an interaction contrast ratio of 9.25 (CI: 3.56; 14.94), which may be consistent with biological interaction.ConclusionsThe majority of children with CP born at term most likely had an antenatal or single cause, suggesting individual susceptibility to an injury. The majority of children born preterm, had combinations or sequences of antenatal and perinatal risk factors as the most likely cause of CP.