Complications more common among preterm infants include the following: Central nervous system: Apneic episodes (see Apnea of Prematurity) Gastrointestinal tract: Poor feeding due to delayed maturation of the suck and swallow mechanism (primary reason for prolonged hospital stay and / or readmission) Hyperbilirubinemia: Caused by immature mechanisms for hepatic bilirubin metabolism and / or increased intestinal reabsorption of bilirubin (eg, if feeding difficulties cause decreased intestinal motility) Hypoglycemia: Caused by low glycogen stores Temperature instability: Some degree of neonatal hypothermia in half of infants (caused by increased surface area to volume ratio, decreased adipose tissue, and ineffective thermogenesis from brown fat) Evaluation of Late Preterm Infants Routine screening for complications There are variations in practice in the care of late preterm infants, particularly with respect to the gestational age and / or birthweight at which infants are routinely admitted to a NICU.