The most advanced level III units, designated level IIIC, which may be located at children's hospitals, have additional capabilities within the institution, including ECMO and surgical repair of serious congenital cardiac malformations that require cardiopulmonary bypass.42–44 It is logical to assume that substantial experience is needed for the best outcomes in patients who require the most advanced support.23,24,45 However, data are not currently available to define this requirement. Concentrating the care of infants with conditions that occur infrequently and require the highest level of intensive care at designated level III centers allows these centers to develop the expertise needed to achieve optimal outcomes and avoids costly duplication of services in multiple institutions within close proximity.