 Neonatal sepsis is an important determinant of adverse neurodevelopmental outcome. The investigators seek to investigate whether neurodevelopmental outcome following neonatal sepsis differs according to whether or not the diagnosis is confirmed by culture. In a secondary analysis of all 3493 infants included in the International Neonatal Immunotherapy Study INIS randomized controlled trial of intravenous immunoglobulin for neonatal sepsis, the investigators will evaluate neurodevelopmental outcomes according to whether or not the sepsis was culture-proven. The primary outcome is death or major disability at two years. In secondary analyses the investigators will determine neurodevelopmental outcomes according to the causative organism identified. Greater understanding of the impact of culture-positivity on long-term outcomes in the setting of clinical neonatal sepsis is essential to better inform parents about the future prospects of their child and to guide patient follow-up. 