Premature infants, defined as those born before 37 full weeks of gestation, face numerous developmental challenges, including learning to feed independently. Oral feeding is an intricate process requiring precise coordination between multiple physiological systems, and an infant born early has not had the necessary time for these systems to fully mature. This developmental immaturity makes the transition to breast or bottle feeding significantly more difficult. The struggle is not due to a single issue but rather a combination of neurological, mechanical, and systemic factors that collectively impede the ability to consume adequate nutrition safely and efficiently.
Immaturity of the Suck-Swallow-Breathe Reflex
The primary challenge preterm infants face is the lack of synchronized timing within the suck-swallow-breathe reflex, a complex neurological circuit required for safe oral intake. This coordination typically begins to mature around 32 to 34 weeks post-menstrual age, meaning infants born earlier lack the innate programming to perform these actions simultaneously. Without this mature coordination, the infant’s sucking pattern often becomes disorganized and inefficient, characterized by bursts of sucking followed by prolonged pauses.
This disorganized pattern leads to poor pressure generation and inadequate milk transfer, making the feed lengthy. The lack of coordination significantly increases the risk of aspiration, where milk enters the airway because the swallow is not timed correctly with the breath. The infant often stops sucking to catch their breath, interrupting the rhythm and preventing a sustainable feeding pace.
Sucking requires a substantial expenditure of energy, which an immature infant often cannot sustain for long periods. Because the process is effortful, the infant quickly develops fatigue, limiting the duration of the feed. Short, inefficient feeds mean the infant burns too many calories relative to the nutrition ingested, creating a cycle of poor weight gain and exhaustion.
Compromised Digestive System Function
Beyond the mechanical challenges of milk intake, the preterm infant’s gastrointestinal tract is often anatomically and functionally immature. The stomach is small relative to their high caloric needs, requiring frequent, small feeds. This reduced capacity limits the volume of milk they can comfortably tolerate, potentially preventing them from reaching their necessary daily intake.
A common issue is gastroesophageal reflux (GER), or “spitting up,” which occurs because the lower esophageal sphincter is weak. This sphincter normally keeps stomach contents contained, but its immaturity allows milk and acid to flow back up. This causes discomfort, interrupts the feeding process, and may cause the infant to refuse the bottle or breast.
Furthermore, the motility of the gut is often slow, referred to as delayed gastric emptying. The muscles lining the stomach and intestines are not yet coordinated enough to push food through the digestive tract efficiently. This slow movement leads to abdominal distension and prolonged feelings of fullness, reducing the infant’s appetite for the next scheduled feed.
Influence of Systemic Medical Conditions
The challenge of feeding is magnified by underlying systemic medical conditions common in premature infants, which divert energy away from the feeding task. Respiratory conditions, such as chronic lung disease or bronchopulmonary dysplasia (BPD), significantly increase the work of breathing. When the body expends excessive energy just to move air, the infant has fewer metabolic resources left for the sustained effort of sucking and swallowing.
This increased respiratory effort often results in oxygen desaturation during feeding, causing the infant’s oxygen levels to drop. The infant must stop feeding to recover oxygen status, leading to frequent interruptions and incomplete feeds. Similarly, cardiac issues common in prematurity, such as a patent ductus arteriosus (PDA), put additional strain on the circulatory system.
These cardiovascular challenges require a high expenditure of calories to maintain bodily function, predisposing the infant to extreme fatigue during strenuous activity, including feeding. Ongoing infection or general illness also redirects metabolic resources toward fighting the disease. In these cases, the body prioritizes oxygenation and fighting infection, making feeding a secondary and often unsustainable function.
Developing Oral Motor Skills and Sensory Tolerance
Preterm infants often develop difficulties related to their learning environment and the quality of their oral muscle movements, separate from physical limitations. Many require prolonged periods of non-oral feeding, such as feeding tubes, which can lead to a lack of positive oral experiences. Because the mouth and throat have been associated with necessary but unpleasant medical procedures like suctioning or intubation, some infants develop an oral aversion.
They may learn to associate oral stimulation with discomfort or pain, causing them to resist the introduction of a nipple or pacifier. This sensory processing issue results in hypersensitivity to various stimuli. They may react negatively to the texture of a nipple, the temperature of the milk, or the flow rate, perceiving them as overwhelming or irritating.
The quality of muscle movement also presents a challenge. Many preterm infants exhibit hypotonia, or low muscle tone, especially in the facial and jaw muscles. This low tone makes sustained jaw closure and necessary cheek strength difficult to achieve, compromising their ability to maintain a strong, consistent suck. Even if the reflex coordinates, the physical musculature may not be strong enough to execute the movement effectively, contributing to poor endurance and efficiency.