Neonatal sepsis commonly leads to meningitis due to the immature immune system and the ability of pathogens to cross the blood-brain barrier in neonates. This complication is critical because it can cause severe neurological damage if untreated. Early identification and treatment of meningitis in septic neonates are essential to reduce morbidity and mortality. Hypoglycemia, polycythemia, and congenital heart disease are not direct complications of neonatal sepsis. Therefore, meningitis is the most critical and frequent complication to monitor in these patients.

Reference: Nelson Textbook of Pediatrics, Kliegman RM, 21st Edition.