Pediatric Nutrition in Practice

Preterm and Low-Birth-Weight Infants 215

3

Nourishing Preterm and Low-Birth-Weight
Infants

Provision of nutrients has to overcome the im-
maturity of the intestinal tract; this is the most
important physiological limitation in these in-
fants. This necessitates the use of parenteral nu-
trition during the early days and often weeks of
life. Although parenteral nutrition carries risks,
especially that of infection, failure to provide nu-
trients parenterally would place these infants at
high risk of impaired neurodevelopment or im-
paired host defenses. Immaturity of the intestinal
tract is also the main reason why preterm infants
are susceptible to necrotizing enterocolitis
(NEC). While nutrients are provided parenter-
ally, small trophic feedings (gastrointestinal
priming) are given with the sole purpose of stim-
ulating the intestinal tract to undergo matura-
tion. Breast milk is the most effective and safest
feed to bring about intestinal maturation. Once
maturation has occurred, nutrients can be deliv-
ered enterally and parenteral nutrition may be
phased out.
Nutritional support of preterm infants oc-
curs in four distinct phases, each with its own
risks and challenges. During the early phase,
nutrients are almost exclusively provided via the
parenteral route, while small enteral feedings
(gastrointestinal priming) are used to prod the
immature intestinal tract into undergoing mat-
uration. During the subsequent transition
phase, enteral feeding is slowly advanced as the
intestinal tract shows evidence of maturation,
and parenteral nutrition is gradually phased
out. During the late phase, infants are on exclu-
sive enteral feeding and are expected to grow
normally. If provided the necessary nutrients,
preterm infants may also show catch-up growth,
t hat is, t hey may be ma k ing up for lost time dur-
ing the early phase. Preterm infants continue to
have special nutritional needs after discharge
from hospital.

Early Phase

During the immediate postnatal period, the ob-

jective of nutritional support is twofold: to pro-

vide an uninterrupted flow of nutrients so that the

anabolic state that existed in utero can continue

with minimal or no interruption, and to stimulate

the immature gastrointestinal tract to undergo

maturation. As gastrointestinal maturation pro-

gresses, a gradual shift occurs from exclusive par-

enteral nutrition to predominant, and finally ex-

clusive, enteral nutrition. The early phase ends

when enteral feedings exceed about 20 ml/kg/day.

Parenteral Nutrition

In immature infants, parenteral nutrition must be-

gin immediately (within 2 h of birth), and as a min-

imum must provide glucose, amino acids, electro-

lytes, Ca, P and Mg (starter parenteral nutrition)

until full parenteral nutrition can be started. It is

acceptable for the amount of amino acid to be less

than 3.5 g/kg/day for a few days. Initiation of lipid

emulsion is somewhat less urgent, and a delay of 24

h is acceptable. The initial rate should be 1.0 g lip-

ids/kg/day. The efficacy and safety of parenteral

nutrition starting immediately after birth have

been established [3]. Full parenteral nutrition

should be maintained until enteral feedings of 20

ml/kg/day are regularly tolerated. As the feedings

are increased, the amount of parenteral nutrition

is tapered, with total (parenteral plus enteral) in-

take of nutrients always remaining at full level.

Enteral Nutrition

The anatomically and functionally immature in-

testine can undergo maturation in a relatively

short time if the necessary stimulation is provided

in the form of trophic feedings (gastrointestinal

priming). Gastrointestinal priming should be

started on the first day of life. Feeding volumes

initially may be as low as 2 ml every 6 or 4 h. Stim-

ulation of the gut is initially the sole objective of

enteral feeding. Motility serves as a marker of gut

maturation and is monitored clinically by assess-

ment of gastric residuals. As gastric emptying im-

Koletzko B, et al. (eds): Pediatric Nutrition in Practice. World Rev Nutr Diet. Basel, Karger, 2015, vol 113, pp 214–217
DOI: 10.1159/000360342