How does the foetal gastrointestinal tract develop in preparation for enteral nutrition after birth?

Abstract

At birth, the gastrointestinal tract (GIT) must be able to cope with the shift from parenteral nutrition before birth (via the placenta) to enteral nutrition after birth (oral colostrum/milk intake). In preparation for this event, the GIT grows and matures very rapidly in the weeks before birth. A series of studies in foetal pigs and sheep have shown that both hormonal and luminal factors influence this rapid phase of GIT development in farm animals. Among the potential hormonal regulators of development, cortisol plays a pivotal role. Thus, the normal developmental increases in stomach acid and gastrin secretion, and in certain enzyme activities (chymosin, pepsin, amylase, lactase, aminopeptidases), are stimulated by circulating cortisol. Cortisol also affects the intestinal absorption of immunoglobulins at birth but has limited effects on the GIT in the postnatal period. Ingestion of amniotic fluid by the foetus and of colostrum by the neonate also modulates GIT growth and enzyme activities. These effects may be mediated via luminal actions of growth factors, hormones and nutrients present in the fluids. However, luminal influences on the developing GIT are less pronounced in the foetus than in the neonate. In conclusion, both circulating and luminal factors affect prenatal GIT development to ensure that the foetal GIT is sufficiently mature to support the dramatic changes in nutrition that occur at birth.