Increasing prevalence of cerebral palsy in children born very preterm in Denmark.

Aim: To analyse the rising prevalence of cerebral palsy (CP) in children born preterm in Denmark.

Method: We included all live-born children born preterm in Denmark from 1997 to 2013. The prevalence of CP in children born preterm was categorized by gestational age and correlated with neonatal mortality and changes in clinical factors.

Results: Among 70 876 children, 824 (1.2%) had CP. The overall CP prevalence in children born preterm decreased substantially until 2001, from when it increased annually by 2.8% (95% confidence interval 0.6-5.0). When categorized, the prevalence only increased significantly in children born very preterm (gestational weeks 28-31). Neonatal mortality rates decreased steadily at all gestational ages during the entire study period. Clinical factors that changed during the study period were increasing numbers of high-risk pregnancies, maternal obesity, emergency caesarean sections, neonatal admissions, and usage of assisted ventilation.

Interpretation: The increasing prevalence of CP in children born preterm was driven by the subgroup born very preterm and matched their decrease in neonatal mortality. In similar population studies, decreased mortality was not followed by increased CP prevalence. An increase in clinical risk factors was unlikely to explain our findings, but more active neonatal life support may have played a role.