Pediatric surgeons who specialize in neonatal surgery have advanced training in the surgical and post-operative treatment of sick and premature newborns aged less than four weeks old. These patients receive their care in the hospital Neonatal Intensive Care Unit (NICU). Surgeries on neonates typically focus on correcting birth defects, including but not limited to urological, chest and abdominal abnormalities. Some newborns require special medical care for conditions such as sepsis or possibly a birth injury such as neonatal asphyxia (a disruption of oxygen to the brain). Also referred to as neonatologists, neonatal surgeons undergo four years of medical school training followed by a three-year pediatric residency and another three years of specialized training in newborn intensive care. They are certified by both the American Board of Pediatrics and its sub-board of Neonatal-Perinatal Medicine.