Inclusion Criteria:  Extremely preterm infants less than 29 weeks' gestation Infants hospitalized for at least the first 30 days of life in the neonatology department of the Croix-Rousse Hospital in Lyon Infants born between January 1, 2013 and December 31, 2016  Exclusion Criteria:  Infants with a congenital heart, lung or brain malformation Infants with a neuromuscular disease Infants with a genetic disorder Infants who died before the age of 24 months corrected age Infants lost to follow-up or with incomplete data at 24 months corrected age