“…Our work is unique, as while small studies have investigated hospitalisation of children discharged from NNUs in specific populations, such as those born very preterm, 18 19 or children admitted to PICU during (but not after) their neonatal stay, to the best of our knowledge, this is the first study to link NNU and PICU data on a population level for individual children. The NNRD and PICANet are national data sources with high levels of ascertainment, completeness and data quality including for personal identifiers, providing potential for high levels of linkage success, although we cannot quantify how many children, if any, were missed.…”