Identifying Congenital Heart Disease in Denmark

Exposure was defined as having a CHD–either simple and complex. Using the DNPR we identified all Danish children diagnosed with CHD between 1994 and 2012. A diagnosis of CHD was defined as ICD-10 codes; DQ20–DQ26. The 10th edition of the ICD has been used since 1994, hence our start of the study period at this point in time. The CHD diagnoses were grouped into either complex CHD or simple CHD in line with previous studies (20 (link)). If a child had more than one diagnosis of CHD, we included the most severe diagnoses given at the earliest point in time. To increase the diagnostic validity only children with a CHD diagnosis issued at a University Hospital were included (21 (link)).