A fetus's gastrointestinal (GI) tract is fully formed at 20 weeks, however it is not fully functional at that time. How well a baby's GI tract functions is related to the baby's gestational age. Diagnosing an immature GI tract, is a diagnosis of elimination, meaning similar conditions must first be ruled out.
All the parts of the GI tract are formed, such as the stomach and the small and large intestines, but some mechanisms needed for the GI tract to begin functioning have not yet developed. For example:
- Peristalsis, the normal intestinal contractions that propel food through the system, won’t start working well until about the 29th week.
- The baby’s body may not yet be producing enough of the enzymes needed to digest milk and formula.
- The coordination skills for sucking and swallowing are not usually present until about the 33rd week.
An immature GI tract is a developmental phenomenon, not a disease. There is nothing “wrong” with the digestive system except that it does not yet know how to function properly. Like so much in the world of prematurity, how well or poorly a baby’s GI tract does function is a reflection of their gestational age. The more immature a baby is, the more likely there will be problems with the function of the GI tract. Mildly premature babies are more likely to have only minor and temporary problems with the GI tract, if any.
Diagnosing an immature GI tract
Diagnosing an immature GI tract is a diagnosis of exclusion. In other words, since the signs and symptoms of an immature GI tract are initially the same as some digestive conditions, those other conditions will be ruled out first. Conditions to be ruled out before an immature GI tract is diagnosed include septic ileus, necrotizing enterocolitis (NEC), and congenital malformations. These conditions are discussed further down the page.
Initially, a baby with an immature GI tract will have feeding intolerances. These include vomiting food, stomach bile, or both; abdominal distension, where the baby’s belly appears abnormally large; reduced or absent bowel sounds; and reduced or absent stool. In some cases, the baby will also appear generally unwell.
Abdominal X-rays will be taken in an attempt to rule out other possible causes of these symptoms, such as NEC and abdominal malformations. Both these conditions can have similar symptoms to those created by an immature GI tract. If no malformations or features expected with NEC are detected with X-rays, it is likely that the symptoms are caused by an immature GI tract.
As with all feeding problems, blood tests will be conducted. Signs of infection, such as an abnormal white blood cell (WBC) count, will be checked. Other tests will look for evidence of electrolyte imbalances, hypoglycemia, and metabolic acidosis. These are all metabolic signs of a GI tract that is functioning poorly or not at all.