Development of the Gastrointestinal Tract in Newborns as a Challenge for an Appropriate Nutrition: A Narrative Review

Abstract

The second and third trimesters of pregnancy are crucial for the anatomical and functional development of the gastrointestinal (GI) tract. If premature birth occurs, the immaturity of the digestive and absorptive processes and of GI motility represent a critical challenge to meet adequate nutritional needs, leading to poor extrauterine growth and to other critical complications. Knowledge of the main developmental stages of the processes involved in the digestion and absorption of proteins, carbohydrates, and lipids, as well as of the maturational phases underlying the development of GI motility, may aid clinicians to optimize the nutritional management of preterm infants. The immaturity of these GI systems and functions may negatively influence the patterns of gut colonization, predisposing to an abnormal microbiome. This, in turn, further contributes to alter the functional, immune, and neural development of the GI tract and, especially in preterm infants, has been associated with an increased risk of severe GI complications, such as necrotizing enterocolitis. Deeper understanding of the physiological colonization patterns in term and preterm infants may support the promotion of these patterns and the avoidance of microbial perturbations associated with the development of several diseases throughout life. This review aims to provide a global overview on the maturational features of the main GI functions and on their implications following preterm birth. We will particularly focus on the developmental differences in intestinal digestion and absorption functionality, motility, gut–brain axis interaction, and microbiomes.

Association between Abnormal Antenatal Doppler Characteristics and Gastrointestinal Outcomes in Preterm Infants

“…According to the results of the multivariable GLMs, a lower GA and formula feeding are independent risk factors for adverse GI outcomes. The anatomical and functional immaturity of the bowel tract affect gut motility, alter the barrier function of the intestinal mucosa, and hinder the adequacy of digestive and absorptive processes [ 35 ], thus increasing the susceptibility of preterm infants to intestinal injury. Consistently with the present results, Kempley et al investigated feeding tolerance and NEC prevalence in AREDF infants < and ≥29 weeks’ gestation, observing a significant increase in adverse GI outcomes in the more preterm subgroup [ 36 ].…”

Influence of Maternal Body Fat on Levels of Insulin, Insulin-Like Growth Factor-1, and Obestatin

“…During this period, there is postnatal acquisition of functionally mature pancreatic β-cells that secrete insulin (Henquin & Nenquin, 2018). Insulin not only plays an important role in intestinal maturation, but it may also contribute to improve lactase activity (Indrio et al, 2022); however, whether milk derived from an obese mother could condition the infant's development remains unknown (Young et al, 2017). Note.…”

Nutrition Support Practices for Infants Born <750 Grams or <25 Weeks Gestation: A Call for More Research

“…A review of the prolific growth and organogenesis in fetuses is truly astonishing and must be considered in the context of nutritional research and clinical care in an extreme subpopulation. For example, (1) the fetal brain is estimated to grow at a rate of 250,000 nerve cells per minute to achieve more than 100 billion nerve cells by the time of normal term birth [ 9 ], and (2) the gastrointestinal tract contains hundreds of millions of neurons [ 10 ] and grows from approximately 125 to 200 to 275 cm from 20 weeks to 30 weeks and finally to term gestational age [ 11 ]. Consequently, an inappropriate delivery of nutrition during these critical periods impairs the potential for proper or complete organ development and function.…”