Providing adequate nutrition for the healthy full-term newborn is relatively easy; breast milk or formula is sufficient for the first six months of life. Although the full-term infant's organ systems are relatively mature, the gastrointestinal tract is often stressed by the demands of rapid growth, and feeding difficulties, such as gastroesophageal reflux, colic, milk allergy, and constipation, may occur that necessitate special handling. The small preterm infant, however, has many urgent nutritional needs; management is usually complicated by the fact that the infant's immature organs may be unable to cope with enteral feedings. Thus, total parenteral nutrition is necessary, with extensive laboratory monitoring of metabolic functions and precise attention to detail to avoid a prolonged period of partial starvation.