1 Department of Neonatology, Burgos University Hospital, Avda Islas Baleares s/n, 09006, Burgos, Spain. Electronic address: jusoru@hotmail.com.
2 Pediatric Research Institute - Sant Joan de Déu Hospital, Barcelona University, Passeig Sant Joan de Déu, 2, 08950, Barcelona, Spain. Electronic address: agarciaalix@hsjdbcn.org.