A significant decrease in CP prevalence since the 1980s up to the birth-year period 1995–1998 has been reported from this long-term study of the panorama of CP in Sweden (3). This is mainly due to the decrease in CP in children born preterm, a finding also recognized in other population-based studies (13). This overall trend has now ceased, due to an apparent rise in CP in children born at term, while CP in children born preterm is still decreasing; now also in the group born before 28 weeks of gestation. More children were the result of stimulated pregnancies or in-vitro fertilization before. However, studies have shown that IVF in itself does not increase the risk of CP in the infant, but it is involved in the increased risk of preterm birth (14,15). The previous male predominance was also absent. A similar, uniform gender distribution has been reported from Iceland (16). In this study, the uniform distribution of gender was due to the female predominance in term-born children. Looking back to the 1970s, no trend regarding gender distribution could be seen. The expected male predominance was, however, still found in preterm children. The increase in dyskinetic CP since the beginning of the 1990s continued. Children born at term now dominate the panorama of CP more than before, and dyskinetic CP is a CP type characteristic of children born at term and with depressed vital signs at birth (17). A recent report from the SCPE network of Europe has also indicated an increasing trend regarding dyskinetic CP in children with normal birth weight (18). The decrease in preterm CP has previously correlated well with a decrease in bilateral spastic CP (4,5). This is no longer the case, as there is now an increase in children with severe bilateral spastic CP, or tetraplegia, born at term. However, there is still a decrease in bilateral spastic CP in children born preterm. The advances in maternal and peri-/neonatal surveillance and care are probably responsible for the latter. The risk factors’ characteristic of children with perinatal adverse events born at term has still not been sufficiently addressed. A well known aetiological factor in dyskinetic CP is HIE in infants born at term or near term. It can be speculated that this factor has not decreased, and that children suffering from HIE may survive to a larger extent than before. The cooling of the head or body after asphyxia shows promising results in reducing morbidity and mortality (19,20), whereas pharmacological treatment is less well developed, despite intensive research into the mechanisms of perinatal brain damage (21,22). Recently, it was suggested that erythropoietin improved the outcome after ischaemia (23). A genetic contribution to the risk of CP has been detected by Gibson et al. in a population-based study (24), whereas infectious or thrombophilic factors, for example, are highlighted by others (25,26). The origins of CP remain only partially explained, although the description and dating of the lesions are increasingly detailed, mainly due to the advances in neuroimaging (27–30). In this study, CT and/or MRI had been performed in 90% of the children. CT was the only imaging modality in 74 children which may be insufficient. In the 14 children with normal finding on CT, an MRI might have revealed lesions explaining the CP. MRI was preferred to CT in the consensus statement about the diagnostic assessment of cerebral palsy by the American Academy of Neurology (31). In this study, CP was considered to be prenatally derived in more than one-third, while in about 40%, indications of a peri-/neonatal origin were found. Slightly fewer children were assigned to the unclassified group, 21% compared to 30% in the previous cohort of children born in 1995–1998. The combination of risk factors to create a causal pathway is still a relevant concept (32) and, in combination with MRI, the plausible time frame of injury may be narrowed.
In conclusion, the total prevalence of CP in western Sweden ceased to decrease and was found to be on a par with other European countries. While the prevalence of CP in children born preterm continued to decrease, the children born at term now dominate more than before, including a typical subgroup of term-born children, namely those with dyskinetic CP.