Abstract

ObjectiveThe aetiology of childhood cancer remains largely unknown but recent research indicates that uterine environment plays an important role. We aimed to examine the association between the Apgar score at 5 min after birth and the risk of childhood cancer.DesignNationwide population-based cohort study.SettingNationwide register data in Denmark and Sweden.Study populationAll live-born singletons born in Denmark from 1978 to 2006 (N=1 771 615) and in Sweden from 1973 to 2006 (N=3 319 573). Children were followed up from birth to 14 years of age.Main outcome measuresRates and HRs for all childhood cancers and for specific childhood cancers.ResultsA total of 8087 children received a cancer diagnosis (1.6 per 1000). Compared to children with a 5-min Apgar score of 9–10, children with a score of 0–5 had a 46% higher risk of cancer (adjusted HR 1.46, 95% CI 1.15 to 1.89). The potential effect of low Apgar score on overall cancer risk was mostly confined to children diagnosed before 6 months of age. Children with an Apgar score of 0–5 had higher risks for several specific childhood cancers including Wilms’ tumour (HR 4.33, 95% CI 2.42 to 7.73).ConclusionsA low 5 min Apgar score was associated with a higher risk of childhood cancers diagnosed shortly after birth. Our data suggest that environmental factors operating before or during delivery may play a role on the development of several specific childhood cancers.