Pediatric Nutrition in Practice

84 Lentze

the first tube has a length of 4 mm from the
mouth to the cloaca. During pregnancy, it elon-
gates about 1,000-fold until full term. The sto m-
ach at term has a volume of about 30 ml, the small
intestine a length of 250–300 cm, the large intes-
tine a length of 30–40 cm. Between the 9th week
of gestation and birth, the small intestine under-
goes extraordinary changes from a primitive strat-
ified epithelium of undifferentiated epithelial cells
into a fully differentiated organ with villi and
crypts [1]. The formation of Peyer’s patches starts
at 16–18 weeks of gestation when the first lympho-
cytes are seen in the lamina propria [2].
Parallel to the morphological changes during
fetal development, the digestive and absorptive
functions of the gastrointestinal tract begin to

appear at the 10th week of gestation and fully ex-

press their activities between the 26th week of

gestation and term, or within the first month of

life.

The brush border enzymes lactase, maltase-

glucoamylase and sucrase-isomaltase are first de-

termined at the 10th week of gestation ( fig. 1 ).

Whereas sucrase-isomaltase reaches its full ac-

tivity already by the 25th week of gestation, lac-

tase activity is fully developed by the 32nd week

of gestation [3, 4]. As lactose is the predominant

sugar in breast milk, the possibility exists that

premature babies born before the 32nd week of

gestation might lack full lactase activity when fed

breast milk or a lactose-containing premature

formula. However, the overall lactase activity

05

Detection of first activity

Full activity

10 15 20 25 30 35 40

BBM peptidases

Weeks of gestation

Lactase

Maltase-glucoamylase

Sucrase-isomaltase

Prematures

<1,500 g

SGLT1, GLUT5

Amino acid transporters

Peptide transporters

Fig. 1. Development of brush border enzymes and transporters during fetal life. BBM = Brush border

membrane; SGLT1 = sodium-dependent glucose transporter 1; GLUT5 = glucose transporter 5.

Koletzko B, et al. (eds): Pediatric Nutrition in Practice. World Rev Nutr Diet. Basel, Karger, 2015, vol 113, pp 83–86

DOI: 10.1159/000360320