Department of Paediatrics, University College Hospital, Ibadan.
Preterm deaths are responsible for the highest number of neonatal mortality in Nigeria. Preterm nutrition contributes significantly to overall outcome particularly as it relates to neurodevelopment. Recently, new guidelines for enteral feedings in premature infants were issued by the American Academy of Paediatrics and European Society of Pediatric Gastroenterology, Hepatology and Nutrition Committee on Nutrition. Nevertheless, in clinical practice it is often difficult to attain suggested intakes at all times. The situation is worse in Nigeria where there are no specific national guidelines and recommendations derived from local data targeting Preterms. There is a high possibility of significant potential cumulative nutritional deficits occurring in Nigerian preterms. The inevitable suboptimal intake contributes significantly to the incidence of neonatal diseases and outcome. This review describes practical ways of optimizing nutritional intake in these vulnerable neonates with reference to Nigerian situation. Understanding the preterm gut, initiation of parenteral nutrition, need for minimal enteral feeds, ensuring adequate macro and micronutrients intake and need for follow up are discussed. There are limitations to the practice of the recommended preterm nutrition in Nigerian settings, nevertheless the interventions like early commencement of minimal enteral feeds and preference for human breast milk should be practiced optimally. Hence, all health professionals should acknowledge that preterm nutrition may be an emergency and need to improve their knowledge on when and how to achieve optimal feeds in them. There is a dare need through both clinical practice as well as research, to reduce nutritional deficits in these vulnerable infants.
Dr. A.I. Ayede
Department of Paediatrics
University College Hospital
Preterm deaths are responsible for the second highest number of neonatal mortality in Nigeria1. Preterm nutrition contributes significantly to their overall outcome particularly as it relates to neurodevelopment2. Feeding issues in preterm infants are a growing concern for neonatologists because of its contribution to outcome and the fact that attainment of independent oral feeding is one of the prerequisites for hospital discharge following their management. Weight gain, length and occipitofrontal circumference are routine parameters measured during the follow up management of preterm infants and their nutrition plays significant roles in these parameters. With the increase in sur vival of infants born preterm, understanding their nutritional needs have become paramount to newborn health care providers particularly neonatologists, paediatric gastroenterologists and neurologists who follow up these babies on long term basis. Research over the last decade has begun to shed light on the development of oral feeding skills in these infants as they mature. This has increased understanding of their limited skills at varying postmenstrual ages. Such knowledge is crucial in clinical practice as expectations of these infants’ oral feeding performance must take into account the ever-changing level of maturity of their skills. The role of gut immaturity in preterm infants is crucial and forms the basis for the mode of feeding, type of nutrient composition, combination and when to feed. The American Academy of Paediatrics and European Society for Paediatric Gastro- enterologist have given preterm recommendations based on in utero accretion growth rate and available data.
These recommendations however have their challenges even in developed countries and this is worse in developing countries like Nigeria1. This article reviews the practical aspect of these recommendations and discusses the challenges of implementing such in Nigeria.
The preterm gut peculiarities The human fetus receives nutrients, growth factors and immunoglobulins via active or passive placental transport. The functional development of the gastrointestinal tract begins in utero and continues into infancy while the fetal gut is anatomically complete by 20-22 weeks after conception. Nutrient transport systems are in place by 14 weeks for amino acids, 18 weeks for glucose and 24 weeks for fatty acids. Peristalsis begins at 28-30 weeks while coordination of suck, swallow and breathing is at 32-34 weeks. Colonization of the gut by bacteria and the introduction of nutrients into the gut affect postnatal gastrointestinal and immunological development. Swallowing of amniotic fluid nourishes the fetal intestine and prepares this organ for birth. Preterm delivery interrupts the transfer of these factors that are critical to prepare and protect the newborn infant from bacteria that will colonize the intestinal tract postnatally3-5. Preterm infants have anatomic and functional limits to the digestion and tolerance of enteral feeds. Oesophageal peristalsis is immature and bidirectional in preterms with forward movement of food to the stomach near term6. Intestinal motor activity is also immature and disorganized in preterm compare to term infants. Coordinated mature gastrointestinal motility and peristalsis with feeding develop in the preterm between 33 weeks to term. The more preterm a baby is, the greater the delay in passing the first stool. Enterokinase which is the rate limiting enzyme in the activation of pancreatic proteases has only 20% of term baby’s activity in the preterm gut. Nevertheless, the preterm is able to digest and absorb protein efficiently because the protein digestion is aided by the activity of brush border and cytosolic peptidases. Carbohydrate absorption is on the other hand limited by the relative lack of lactase which is responsible for the breakdown of lactose into glucose and galactose. This lactase activity in preterm less than 34 weeks has about 30% of the activity seen in term babies. The relative lack of pancreatic lipase and a small bile acid pool size in preterm predispose them to malabsorb 10 – 30% of dietary fat7.
Preterm nutritional recommendations Breast milk is the preferred source of nutrients for newborn infants including the preterm, and the number of nutrients found in human milk is recommended as a guideline in establishing the minimum and maximum levels in infant formulas8. Sources of nutrient recommendations for preterm infants include the American Academy of Pediatrics Committee on Nutrition(AAP – CON), the European Society of Paediatric Gastroenterology, Hepatology and Nutrition Committee on Nutrition (ESPGHAN – CON) and the Reasonable Ranges of Nutrient Intake published by Tsang and Colleagues. The overall goal is for the growth of the postnatal preterm infant, both their anthropometric indices and body composition to be the same as the normal fetus of the same gestational age growing in its mother’s uterus9. These recommendations are based on the expected intrauterine growth rate, breast milk nutrient content, higher nutritional needs in preterm infants and data from normal biochemical parameters reflecting adequate intake.
Proteins and amino acids
Metabolic balance studies support a need for higher protein intakes in the growing preterm infant than in the term infant. The human milk is inadequate to meet the recommended 3.5 to 4g/kg/day for preterm babies10. Protein supplementation is beneficial for the growth of bone, brain and lean body mass unlike excess energy that leads to increased fat deposition11. Neurodevelopmental outcomes have been shown to be better in preterm infants fed with human milk fortified with protein and energy. These beneficial effects were even noted to have extended to adolescents whose brain size, caudate nucleus and intelligence quotient (IQ) were found to be directly proportional to their protein and energy intake during postnatal period12-15. Growth rate of the lean body mass is determined directly by the essential amino acids intake. Normal growth, energy metabolism and the immune function are known to depend on the availability of these essential amino acids.
Fetal fat deposition occurs in the last 12 – 14 weeks of gestation, thus the preterm infant are deficient in fat which is necessary for energy and thermogenesis. Dietary fats are important to sustain growth, provide essential fatty acids and promote the absorption of fat-soluble vitamins. Newborn infants absorb fat less efficiently than older children and fat digestion and metabolism is even less efficient in preterm infants. Lingual and gastric lipase as well as mammary gland lipase all compensate for the deficient pancreatic lipase. Current recommendations for dietary fat consist of 40% -52% of total calories which is equivalent to 4.4 – 5.7g/100kcal. Breast milk contains adequate arachidonic acid (AA) and docosahexaenoic acid (DHA) with the normal as 5 – 20mg/dL16.
The predominant carbohydrate in human milk is lactose, a disaccharide composed of glucose and galactose. Glucose production rates among pre-term infants at about 28 weeks’ gestation average about 6– 8 mg/min/kg while among term infants average 3– 5mg/min/kg17,18. Preterm infants in thermoneutral environment need 40 – 60kcal/kg/day to maintain body weight once adequate protein intake is achieved. These preterm infants need additional calories to maintain growth and the more preterm the infant is, the higher the calories required to achieve normal growth. Most preterm infants will attain adequate growth with calories of 130 – 150kcal/kg/day.