Neonatal Gastrointestinal Adaptation Processes

Neonatal Gastrointestinal Adaptation Processes

In fetal life the placenta is performing the function of the gastrointestinal system. After delivery, newborns must take in, digest and absorb food as placenta no longer performs these functions.


Gastric emptying may be delayed at first in neonates. A neonate’s gastric capacity is about 6 ml/kg at birth. However, it may expand to approximately 90 ml in the first week. Gastric emptying in breastfed newborns is more rapid than the formula fed babies. When milk hits the stomach and fills it, gastrocolic reflex is triggered.

The gastrocolic reflex or gastrocolic response is a physiological reflex that contributes in controlling gastrointestinal motility and peristalsis. This is the one that signals the colon to empty when food hits the stomach. The reason why infants usually pass a stool after feeding is because of the said mechanism.


The newborn’s intestines are quite long in relation to the infant’s size. This length allows for extra surface area of absorption. However, the longer intestines make infants more prone to water loss. That’s why diarrhea is usually observed in infants.

At birth the intestines are sterile. When a neonate is exposed to the extrauterine environment and starts taking in fluids (feeding), entry of bacteria to the intestinal tract occurs. Normal intestinal flora is established within the first few days of life. Bowel sounds, on the other hand, are present within the first few hours.

Digestive Enzymes

Pancreatic amylase, the enzyme responsible for digesting complex carbohydrates, has inadequate levels for the first 4 to 6 months of life. This enzyme can also be produced in the salivary glands but only in low amounts until the third month. Thus, an infant can start taking in complex carbohydrates (such as cereals) by about 4 to 6 months of age due to the said reason. Amylase is also found in breast milk.

Pancreatic lipase is also deficient in newborns. This enzyme is responsible for fat digestion and absorption. Lipase is also found in breast milk making it more digestible than the formula milk.


Meconium – the first stool excreted by the neonate. It consists of particles from the fetal structure such as vernix, skin cells, cells shed from the fetal intestinal tract, bile and other intestinal secretions. The color of this defecated material is greenish black with a thick, tarlike and sticky consistency. This stool accumulates into the fetal GI tract throughout gestation. Neonates usually pass meconium within the first 12 to 48 hours.

Transitional Stool – mixture of meconium and milk stools. Color is greenish-brown and consistency is looser than the meconium. This is the second stool that is excreted by the neonates.

Milk Stools – stools of infants that vary with the type of milk ingested:

  • Breastfed Infants

Breast milk stools are seedy with the color and consistency resembling to that of mustard with a sweet-sour smell. Babies who are breast-fed pass stools more frequently than formula-fed. Normal breastfed newborn passes at least three stools daily.

  • Formula-fed Infants

A formula-fed infant has a pale yellow to light brown stools. The consistency is firmer than the breastfed infants and has a characteristic odor of feces. The infant may excrete only one or two stools daily.

Daisy Jane Antipuesto RN MN

Currently a Nursing Local Board Examination Reviewer. Subjects handled are Pediatric, Obstetric and Psychiatric Nursing. Previous work experiences include: Clinical instructor/lecturer, clinical coordinator (Level II), caregiver instructor/lecturer, NC2 examination reviewer and staff/clinic nurse. Areas of specialization: Emergency room, Orthopedic Ward and Delivery Room. Also an IELTS passer.

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