The aim of the present nationwide cohort study was to describe trends in 1-year mortality in live-born children with congenital heart defects in Norway 1994-2009 and to assess whether changes in the proportion of terminated pregnancies and altered operative mortality have influenced these trends.Medical information concerning all 954 413 live births, stillbirths, and late-term abortions in Norway, 1994-2009, was retrieved from the Medical Birth Registry of Norway, the Cardiovascular Disease in Norway project, the Oslo University Hospital's Clinical Registry for Congenital Heart Defects and the Norwegian Cause of Death Registry. Survivors were followed through 2012.The 1-year cumulative mortality proportion during the study period was 17.4% for children with severe congenital heart defects and 3.0% for children with nonsevere congenital heart defects. The 1-year cumulative mortality proportion among live born children with severe congenital heart defects decreased 3.6% (95% CI: -5.4, -1.5) per year. The total mortality of severe congenital heart defects was unchanged when including stillbirths and late-term abortions with severe congenital heart defects. The proportion of stillbirths or terminated pregnancies with severe congenital heart defects among all pregnancies with severe congenital heart defects, was on average 8.8% over the entire period with an annually increase of 16.6% (11.4, 18.0). The mean operative mortality in children with severe congenital heart defects was 8.4% and decreased by 9.0% (-11.9, -5.9) per year.The 1-year mortality of severe congenital heart defects among live births, 1994-2009, declined in Norway. The downward trend in mortality may be explained by a more frequent use of termination of affected pregnancies, and the reduced operative mortality of severe congenital heart defects.