Feeding the Pre-term (Low Birth weight) Baby
The increasing number of surviving LBW infants that must be fed has heightened the awareness of the problems encountered in meeting their nutritional needs. The importance of adequate early nutritional management of the LBW infant can be illustrated by considering the energy metabolism of the fasted infant. In such infants, the ultimate determinants of the length of time they can survive depend on the adequacy of hydration, and the available endogenous stores of fat and protein.
The most generally accepted goal for nutritional management of the pre-term (or LBW) infant is to provide sufficient amounts of all nutrients to support continuation of the intrauterine growth rates. But there is currently a new problem of feeding the small pre-term baby. The common practice of feeding pre-term infants with human milk was abandoned some 50 years ago, following the demonstration that protein intakes that are higher than those provided by human milk resulted in a greater rate of weight gain. It is natural that once feeding has become established in a baby weighing 1 kg or less, it should be given sufficient food to enable it to grow at the same rate as it would have done had it not been born. It is also known that breast milk is best in most circumstances. But for the pre-term babies, however, breast milk is inadequate in several respects. The growth rates of these babies fed human milk are considerably lower than those of infants fed formulas. This can be ascribed, in part, to the relatively low protein concentration of human milk. There is also evidence to show that breast milk can not supply the infant with as much calcium and phosphorus as it would have obtained from its mother’s circulation. Breast milk also has some short-comings as its sodium content is grossly inadequate. Fortuitously however, milk of mothers who deliver pre-maturely has an appropriately 20% higher protein concentration and supports desirable growth rates in the premature babies. An infant weighing 2,000 g at birth has more extensive endogenous nutrient reserves than one weighing 1,000 g; and an infant weighing 3,500 g has more extensive reserve than one weighing 2,000 g. Thus, the smaller the infant, the more marked is his inability to withstand starvation. The term baby has sufficient reserve to survive a total starvation condition for approximately a month.
For pre-term infants weighing between 0.5 and 1.0 kg, the intake of sodium from breast milk does not meet the requirements for growth, and for infants between 1.0 and 1.5 kg, it barely does so, even if all the sodium intake is absorbed and retained. Furthermore, the amount of iron in human milk is nowhere near enough to meet the requirements, and the amount of copper is almost certainly inadequate. The large reserve of copper in the liver of full-term infant, amounting to more than there is in the rest of the body, accounts for the rising increment, which is needed to meet the copper requirement of the term infant during the first few months after birth. The small pre-term infant lacks these reserves.
Normal Infant Feeding
All babies thrive on their mothers’ milk. While breast-feeding is universal in the rural areas of Africa, its importance has been diminishing in the cities, especially among the “affluent” mothers. In most communities, breast-feeding is universally accepted as the best means of delivering nutrients to the newborn. But a mother must be encouraged to feed adequately, exercise, rest and have freedom from anxiety in order to fulfil this function. Approximately 120,000 kcal are required for the synthesis and secretion of breast milk during the first 6 months of the infant’s life. The increased caloric allowance for the nursing mother, in effect, translates into her ‘eating for two’ human beings. On account of its ready availability, its relative safety and the promotion of enhanced resistance to infection and bonding between the mother and infant, human milk is usually the perfect food for the normal infant. However, infant feeding does not occur in isolation, but as a part of a complex of interlocking social and biological conditions. For example, if a woman must return to work almost immediately, or she dies soon after childbirth, the only practical decision may well be to feed the baby ‘artificially’. On the other hand, an infant who ha s a strong familial history of allergy may have no alternative to breast-feeding. The human intestinal wall is more permeable to cow’s milk than to breast milk, thereby increasing the risk of allergy. Furthermore, since only about 1% of all women who decide to breast-feed experience any kind of failure, it is unfortunate that, in spite of its many positive qualities, there is a general decline in its usage, thus constituting a loss of valuable natural resource that has been well-recognized as a major force in the prevention of malnutrition in children.
Nutrition after birth is a less efficient process than nutrition before birth for two reasons: firstly, there is inevitably more wastage when nutrients are absorbed through the intestines than when they are delivered directly into the blood stream through the placenta; and secondly, but more importantly, a great deal of the energy taken in the milk is used for maintaining body temperature in an environment that is usually cooler than the uterus. During the first two months of life, only about 25% of the total intake of energy goes towards producing new body tissues, and by 4-6 months, the percentage has fallen to 8 – both in breast-fed and bottle-fed babies. Health and nutrition education should be coupled with emphasis on adequate breast-feeding and safer and adequate supplementary feeding with locally available weaning foods. In this regard, it is necessary to convince parents and most Nigerian health workers that the unfortified pap is 90 to 95% water and low in total energy and proteins. Thus, breast-fed infants from populations at risk of PEM should be weaned with reinforced home-made paps as soon as the growth curve begins to flatten (not on account of diarrhea or pyrexia), the baby cries more often than usual, is restless and sleeps less, often waking up intermittently.
The period of neonatal life and early infancy is characterized by rapid growth. But the human infant grows less rapidly than the young of other mammals. For example, a calf doubles its birth-weight in one month; whereas an average baby doubles its birth-weight in 4 to 5 months, and triples it in about 12 months. Birth-weight doubling time is usually considered to take place around 5 to 6 months, but current data indicate a trend towards faster weight gain among babies. Some authors have reported an average birth-weight doubling time of 119 days (3.8 months) for American children. Formula-fed babies doubled their birth weight earlier than did breast-fed ones (113 versus 124 days). However, a general trend towards an increased rate of weight gain in infancy may contribute to later problems of obesity. This rapid growth is brought about by increased muscle mass, growth of organs, expansion of blood volume and linear increase in the long bones. The breast milk alone in the first 3 to 4 months of life supplies the nutrients required to sustain such a growth for practically all children. The composition of human milk therefore provides a clue to the physiological needs for these nutrients and for energy in the infant.
For an infant, food is both a source of nutrients as well as a source of nurture. When a baby is bottle-fed or breast-fed, food and love become synonymous. But the needs of both the mother and her child must be taken into consideration in deciding which mode of feeding is best; and with breast-feeding; encouragement should be given wherever possible.
Soon after birth, but not later than 4 hours, a normal full-term healthy baby should be put to the breast. Such a baby is capable of being put to the breast immediately after birth, however, and this should be encouraged. If no breast milk is forthcoming, as in the case of a baby whose mother dies soon after child-birth, the baby may be put to 10% dextrose, or 5% sucrose or plain water. However, no effort should be spared to initiate breast-feeding.
Eating is an activity in which babies play an active role, unlike bathing, clothing, etc. This activity involves three mechanisms: rooting (searching for the nipple), sucking (continuous or intermittent) and swallowing (well-coordinated with breathing, allowing milk to go to the esophagus instead of the lungs). Nutritive suckling behavior in the new born is affected by obstetric sedation, with the infant suckling at significantly lower rates and pressures and consuming less. This lack of responsiveness should be recognized quickly since this can interfere with nutrient intake and the developing mother-child relationship, as anxiety, tension or frustration, on the part of the mother, can negatively reinforce the infant’s early feeding experience. In the first year of life, an infant progresses from a totally dependent (passive) feeder to that of an active participant with a fair amount of independence. This follows the sequence of head, trunk, gross and fine motor control as the infant’s reflexive behavior becomes voluntary, e.g. chewing and swallowing rather than sucking solid foods, or drinking from a cup.
It is now well-established that the human milk is the best food for infants and will meet the nutritive requirements of early life when it is supplied in sufficient quantity. In general, the breast milk from a well-nourished mother alone is sufficient to meet the infant’s nutritional needs in the first 3 to 5 months of life. Where infant formula must be used, sterilized formulas, which have been processed to simulate human milk, together with vitamins and iron supplements, can also meet the infant’s needs. Growth is rapid and nutrient needs parallel growth. Fortunately, the typical African breast-fed child shows good growth during the first six months which is equal to, or even better than, that of children in the highly-developed countries.
Thus, cow’s milk or skim milk is not the most suitable food for infant feeding. With early attempts at formula-feeding, as much as 95% of infants fed mammalian milk died in the first two weeks of life, due to protein intoxication, diarrhea, dehydration, hyper-electrolytemia and death. Even present attempts are still producing high (50%) mortality rates among artificially fed infants in developing countries (in homes where bacterial contamination or incorrect formula preparations are common). Where there is refrigeration and little or no contamination of water, death from artificial formula feeding may be reduced to a level similar to that of breast-fed infants. In such cases, formulas are usually fortified with vitamins C and D, iron and other nutrients, decreasing the incidence of rickets, scurvy and iron-deficiency anemias such that there is little distinction between individual breast-fed and formula-fed infants. However, breast milk remains the preferred food for the human infants (though mothers who choose to feed their infants with formulas should not be made to feel guilty, once necessary precautions are taken). Human milk contains more lactose, iron, vitamins A and C per unit volume, but less protein, calcium, phosphorus, riboflavin and thiamin than cow’s milk. One must conclude from these compositional differences, that each mammalian milk is adapted to provide the best nourishment for the young of each species.
The debate on when exactly to introduce other foods besides breast milk continues to rage on. Weaning has been defined as the period which extends from the time when the baby is solely breast-fed until he is feeding entirely on the adult diet. Several studies for and against an early introduction of other foods have been presented. Socio-cultural factors are often ignored when this debate is tabled. There is no doubt that the debate is not founded on physiological one but more on the socio-cultural practices. As pointed out in another section of this presentation, the aim of a more reasonable and scientific approach is to allow mothers to make informed choices on how to feed their infants and support them in their decisions. This scientific approach is to observe the following conditions as a guide to the introduction of other foods. When the growth curve begins to falter, and the child sleeps far less than usual because he has to wake up to feed frequently, it might well be a sign that breast milk is no longer adequate. If such a child does not have a fever or a diarrhea, the mother should be encouraged and educated on how to introduce supplementary feeding.
The belief that human milk has a fairly constant composition, especially in terms of its carbohydrate, protein, fat, calcium and iron content, and is little affected by the diet of the mother, and that human milk is the ideal food for the human infant needs to be qualified. A mother whose diet is deficient in thiamin, vitamin A and ascorbic acid, produces less of these nutrients in her milk, and in the case of thiamin, this can lead to infant beri-beri. Nevertheless, the effect of very poor nutrition on a lactating mother is to reduce the quantity, rather than the quality, of the breast-milk. However, many infants also grow well when fed cow’s milk or formulas that are different in composition from human milk (see Table 6.2 below). Although the economic advantages and microbiologic safety of breast-feeding for less developed and less affluent societies are obvious, these factors are less important in affluent, developed societies in which the current generation was fed artificial formulas during infancy. Thus, a more reasonable and scientific approach is to allow mothers to make informed choices of how they wish to feed their infants and support them in their decisions. Although a baby is born with the full complement of oligosaccharidases, starch should not be given to new born infants because the small amount alpha-amylase produced by the pancreas can not be sufficient to hydrolyze the starches. Furthermore, the size of the baby’s stomach is rather too small to accommodate bulky starches.
Highlights of the Table:
Cow’s milk contains more than three times as much proteins as human milk;
Human milk is two times as high in carbohydrates as cow’s milk;
Calcium levels are appropriately four times higher and phosphorus content, six times higher in cow’s milk than in human milk; and
Cow’s milk is approximately four times higher in riboflavin content than human milk.
Breast-Feeding Versus Bottle-Feeding
It was the famous pediatrician, Paul Gyorgy who once remarked that the “cow’s milk is best for the baby cow and the human milk is best for the human babies.” Fortunately, it has been estimated that 90-95% of mothers are fit and capable of breast-feeding their babies. Although, science and industry have combined their skills to produce cow-milk products that contain nutrients in qualities that are similar to those in breast milk, statistical advantages of breast feeding persist. Nevertheless, formulas have been modified to approximate human milk such that little distinction can be observed between the breast-fed and the formula-fed infants. Thus, the overall nutritional superiority of breast milk (its ability to provide the nutrients) over cow’s milk or its products is not in doubt, at least for those who can not afford these products or who do not live under modern conducive conditions. Thus, there is no doubt that none of these products or the milk of other mammals is, overall, as good as the human milk for the human infant. And the breast milk remains the preferred food for human infants; but in the former cases, as in the studies carried out in Boston, rural Sweden and Kuala Lumpur, where the formula has been properly selected and prepared, few differences were noted in the well-being of the breast-fed and bottle-fed infants. Therefore, mothers who choose to feed their infants with formulas should not be made to feel guilty, if they can afford to do it properly.
Breast-feeding gives a safe and protected feeling to the infant and a sense of satisfaction to the mother. It promotes a feeling of closeness to the baby, thus fostering good mother-child relationship. For some nursing mothers, the great satisfaction of providing food for a small new life from one’s own body, coupled with a strong sense of feminine identity and capacity which may be evoked, are powerful incentives to maintain the nursing role for as long as possible. Paradoxically however, these same factors may lead to a wish to remain the sole source of the infant’s food beyond the limits of nutritive reality. Thus, a well-intentioned prolongation of breast-feeding may unwittingly cheat the infant of needed nutrition.
Secondly, there is a reduced likelihood of diarrhea. The stools of infants fed breast milk has lower pH (5.4) than those fed cow milk (6.9). The higher pH permits greater growth of pathogenic bacteria in the GI tract. In the lower socio-economic groups, breast-fed infants have a consistently lower mortality rate, perhaps because the problem of sanitation is eliminated. In addition, constipation occurs less frequently.
- Breast-feeding confers immunity on the child on account of the immunoglobulins(Ig) and other constituents of breast-milk. The human fetus obtains its IgG antibody before birth from its mother’s circulation, but gets its IgA from the colostrum. This colostrum contains about 11.5% IgA; but by the 4th day, this has fallen to 0.75% and in the mature milk, the concentration of IgA is about 0.1%. IgA, among other agents, acts in the intestine and limits the multiplication of bacterial and viral pathogens within the digestive tract. Thus, it promotes a bifido-bacterial flora in the infant’s intestines that is antagonistic to certain pathogens.
Human colostrum and, to a less extent, mature milk, contains other substances which are important for the infant. For example, they contain lactoferrin, which, by binding iron, makes it unavailable to E. coli in the intestine, thus inhibiting their growth. Colostrun also contains other nutrient binder proteins, which act similarly to lactoferrin for such micronutrients as zinc, vitamin B12 and folate.
Thus, the enzymes, hormones, immunological factors (IgA) and other substances in the breast-milk positively affect digestion, absorption and utilization of nutrients as
well as resistance to enteric and respiratory diseases and to allergy. Thus, as a rule, based on the foregoing, there are fewer and less serious illnesses and feeding problems among breast-fed infants.
- Breast milk is readily available and convenient. On a practical basis, breast-feeding eliminates preparation; it is available at a proper temperature and also avoids errors in calculation and in formula preparation.
- The human breast milk is nutritionally superior to any other infant food. For example, an enzyme which aids protein digestion has been found in greater supply in human milk than in cow milk, hence breast-fed infants are rarely constipated. Furthermore, taurine, a rare amino acid involved in the transmission of nerve impulses, particularly in the eye and the beating of the heart is present in the human but absent in cow milk. Also, lactose aids the absorption of Ca, Mg and amino acids. Upon its digestion, it yields galactose which is an essential structural component of the nervous system of the neonate. When the milk of other mammals is used in the formulation of some commercial foods, this lactose become diluted and inadequate. Furthermore some commercial formulas substitute syrup or sucrose for lactose. Since neither of these yields galactose on hydrolysis, a deficiency of galactose may affect the development of the nervous system of the neonate. In addition, the Poly-Unsaturated Fatty Acids (PUFAs) in the human milk is not normally used as a major source of energy, but are incorporated into cell membranes and are the precursors of prostaglandins which are involved in many functions, such as regulating the transmission of nerve impulses and controlling blood pressure and digestive processes. It is therefore undeniable evident that no other food is equal to that of the human milk for the proper nutrition of the child provided a mother has maintained adequate nutrition herself during pregnancy. The nutritional needs of the infant are better met by human milk than by any substitute, and breast milk is yet to be improved upon as a reference standard. Thus, efforts to duplicate human milk by alteration of the components of cow’s milk have not yet been successful. Besides, children who are breast-fed have lower chances of becoming obese than bottle-fed children.
Breast-feeding confers an economic benefit on the family and the nation since breast milk is the only low-cost high protein food of animal origin which is readily available, especially in times of economic recession and restricted importation of baby foods.
(h) Breast feeding has contraceptive effect on, and can delay the return of, ovulation by as much as 5 to 8 months. Thus, wider spacing of children, resulting from breast-feeding is perhaps having a greater influence on population growth than the pill or the IUD. In some cultures, sexual intercourse is forbidden during breast-feeding, thus having an added beneficial contraceptive effect on the mother.
Despite attempts by food chemists to modify the milk of the cow to feed the human baby, which have been largely unsuccessful, not withstanding the claims made by promoters of products, the history of artificial feeding of infants is full of examples of one mishap after another. Products which are promoted as ‘ideal foods’ are withdrawn from the market after a few years later when their short-comings are exposed, only to be replaced by another family of products, which are again, promoted with equal vigor. Nevertheless, epidemiological observations showed that the following health problems occurred following the feeding of such ‘artificial’ milk products:immunity (thus the breast milk protects as well as nourishes, and the mammalian gland performs functions similar to those of the placenta in the intrauterine life).
- there were widespread outbreaks of rickets in the early part of the century;
Militating Factors against Breast Feeding
Breast-feeding may not be encouraging if:
- for any reason, the mother’s milk production is less than half of the infant’s needs;
- the mother suffers from some chronic illnesses such as cardiac disease, tuberculosis, severe anemia, nephritis, epilepsy, leprosy, insanity/psychosis, chronic fevers and the internationally famous AIDS.
- another pregnancy occurs, although hormonal changes brought about by the pregnancy does not stop breast milk flow; it could lead to a maternal depletion syndrome.
- it is necessary for the mother to return to employment outside the home; or
- the infant is weak or unable to nurse because of cleft palate or hare-lip.
- temporary cessation of breast-feeding is indicated when the mother acquires an acute infection which the infant has not yet acquired.
The commonest ‘local’ cause of breast-feeding failu re, however, are mastitis and breast abscess. In such a situation, the breast may become so painful that suckling becomes impossible, and unless the milk is drawn off, especially if the baby suckles the other breast, thereby stimulating milk secretion in both breasts, the condition may become worse. When this condition is promptly treated, it is seldom necessary to stop breast-feeding or nurse the fear that the baby might be infected through the breast milk. On the other hand, failure to institute therapy may result in serious breast abscess formation, which may lead to the death of the infant, either through direct infection or as a result of losing breast milk supply.
In spite of the contra-indications, bottle-feeding has become a major public health problem in the developing world for the following reasons:
Over-dilution of formulas in these economically-depressed areas of the world usually leads to marasmus. Under-dilution can precipitate childhood obesity.
The poor environmental sanitation in such places leads to diarrhea. Thus, danger signals have been sent out by the WHO and other International Agencies regarding the dangers of artificial feeding, especially in the less developed parts of the world.
there were cases of neonatal tetany in the early 50s;
there were reported cases of pyridoxine deficiency also in the late 50s and early 60s;
hemolysis due to vitamin E deficiency were also recorded;
risks of high plasma sodium (hypernatremia) have also been noted in recent years. Furthermore, many of the dangers of artificial feeding arise from errors in reconstitution
(quality of constituted milk varies by as much as 20-30% from that recommended by the manufacturers). In the affluent homes, over-concentration can lead to infant obesity. Thus, the factors responsible for the decline in breast-feeding include Western influence, medical advice and a strong advertisement and promotion of bottle-feeding. The latter being perhaps, the most potent of all. On account of an intensive promotion by manufacturers, and in the absence of a strong professional support for breast feeding, many mothers take to artificial feeding only to find that the family income is inadequate to support the cost of powdered milk (often, costing as much as one-third to one-half of the wages of the family to feed an 8-month old baby). The temptation therefore, is to ‘stretch’ the tin of powdered milk with consequent under-feeding – accompanied by a high incidence of marasmus.
The gut flora of the artificially fed infant is made up largely of E.coli, with some Streptococcus feculis, in contrast to the breast-fed infant in whom the lactobacillus predominates. The E.coli constitutes a reservoir of potential pathogen. The immune factor in breast milk keeps the population of E.coli low until the baby has developed his own
Since successful lactation is a joint endeavor between a mother and her baby, any failure that arises must come from maternal as well as neonatal causes or a combination. For example, failure could be due to severe maternal ill-health, malnutrition, abnormal nipple (retracted, or very large and pendulous), psychosomatic impairment, congenital abnormalities (cleft palate), cerebral birth trauma, severe general infection (septicemia, meningitis, tetanus neonatorum), dehydration fever or hunger diarrhea).
Mothers who keep their babies on the breast alone may subject their babies to “breast starvation”. Now, weaning is the transitional proce ss between breast-fed adequacy and the full adult diet – a time of accustomizing to new foods and to lessening dependency on breast milk. Unfortunately, the weaning foods commonly used in many parts of Africa range from gruel pap (2% low quality proteins), used in Western Nigeria, to boiled yam in the Eastern region of Nigeria and steamed plantain in Uganda. In other parts of the world, cereal- and legume-based weaning foods are the norm. Table 5.2 (shown below) indicates the proximate composition of certain weaning foods.
Gastric motility is poorly coordinated in the first few weeks of life, leading to poor antral mixing and therefore less digestion of solid foods. By the 12th week of age however, intestinal peristalsis of a type seen in older children and adults develops, but it is about one-third slower. This slower transit time may serve to increase exposure time to the intestinal mucosa, thereby improving nutrient digestion and absorption produced by protein metabolism and an excess intake may result in increased morbidity and mortality associated with uremia in the baby.
The average daily requirements of some selected nutrients in the neonatal/early childhood periods are shown in Table
Indeed, intestinal mucosa permeability is greatest during the neonatal period and many large molecules, including proteins, tend to be absorbed intact. The intestinal mucosa alpha-glucosidases (sucrase, maltase, isomaltase) are well developed by 32 weeks of gestation and are present at near adult level at term. Intestinal amylase needed for starch digestion may not reach adequate level until several weeks after birth. However, for the extremely premature infants (27-32 weeks gestation), formulas with less than 60 % of total carbohydrate calories as lactose are generally best tolerated. Although by six weeks, its ability to concentrate solutes is close to adult levels, yet the kidneys have limited ability to dispose of urea
Nutritional Aspects of Growth and Development
Growth is the increase in size, attendant upon development of an organism from embryo to adulthood, and involves changes in functions and body composition. Since the metabolic rate of infants and children is greater and the turn-over of nutrients more rapid than in the adult, the nutritional needs for growth and development are superimposed upon maintenance requirements that are higher than those of the adults. Meeting these requirements of the infants and children must take into account their unique nutritional needs for supporting both the inevitable increase in size (growth) and the changes in the organ function and body composition (development). Unfortunately, the provision of these needs is hindered by the lack of teeth and the limited digestive and metabolic processes.
Although it is useful to make comparisons with stated norms, such as height and weight, it is instructive to note that every infant and child does not, and need not, conform exactly to such norms. Each infant’s growth and development are determined by
- the characteristics acquired from parents,
- the quality of nutrition of the mother during pregnancy, and
- the adequacy of breast-feeding or formula-feeding and the supplements offered throughout infancy.
Development of personality patterns begins at birth and relates closely to feeding habits. Infants who do not receive adequate calories and adequate mothering in the form of emotional warmth, social contacts, physical handling and sensory stimulation tend not to thrive or grow normally. Furthermore, each child is an individual and serves as the best control in the measurement of his own progress. Height and weight are generally compared to charts that depict a normal population. The best prediction (assessment) of normal growth should however be an integrated scientific measurement of body size (anthropometric), body composition and body cells. Anthropometry deals with an evaluation of body size during growth. Though useful to make comparisons with stated norms (height and weight), it is dangerous to expect every infant to conform exactly to such norms.
Although chronological age is used as a point of demarcation, it is the physiological age of a child that determines its nutrient needs. Physiological age is matched by the chemical index of growth, marked by urinary excretion of hydroxyproline (which is a structural component of skin, tendons, cartilage, blood vessels, connective tissue, organ capsule and bone matrix – a rapid synthesis of which takes place during growth and reflected in an increased rate of its excretion). There is no single criterion of physical status which is indicative of the quality of nutrition – only a series of measurements over a period of time are likely to be reliable indicators.
Growth takes place by three processes:
- by an increase in cell number, known as hyperplasia;
- by growth in cell size, or hypertrophy, and
- by an increase in size of the intercellular matrix.
Hyperplasia characterizes very early embryonic growth while hypertrophy begins in later fetal life. The growth of intercellular matrix begins post-natally. Most tissues enlarge through a combination of hyperplasia and hypertrophy. But some (muscle and fat) grow largely by increase in cell size, while others (bones) grow by an enlargement of the intercellular matrix. Patterns of increase in cell number and size in organs and tissues of infants provide an insight into the nature as well as the failure of growth. Thus, cell size and number are indicators of growth, while height is more of a measure of linear or skeletal growth. Increase in the amount of bones, in contrast to cartilage, indicates the degree of maturation.
Several criteria are used to determine whether an infant is well-nourished or not:
- steady gain in height and weight (but some weekly fluctuations are to be expected);
- sleeps well;
- is happy;
- has firm muscles and a moderate amount of subcutaneous fat;
- teeth begin to erupt within 5 to 6 months;
- is vigorous;
- normally eliminates fecal waste for the type of feeding (2 to 3 soft yellow stools per day for breast-fed and 1 to 2 yellow somewhat firmer stools for formula-fed babies).
Infants grow and develop more rapidly during the first year than at any other time of life.
This is exemplified by the fact that
- weight at birth is 3 x 106 times the weight of the ovum;
- weight-gain reaches its velocity peak for the entire life cycle just after early neonatal weight loss.
- birth-weight is doubled in about five months, tripled by one year and quadrupled by three years;
- weight gain is a composite of growth in all body tissues (muscles, bones, fat and organs).
This generalized growth is reflected in the Ponderal Index: Weight/ Height3 x 100. Ponderal Index relates weight to height, which is highest in infancy and early childhood (when weight is greatest, relative to body surface area, length3). The relation of bone weight to body weight is fairly constant throughout life. Growth in length should increase from the birth length to about 50.8 to 55.9 cm by 20% at three months, 50% by one year and 75% at two years. Thus, the growth of a child tapers off after the first year. For example, there is about 300% increase in weight gain in the first year, but only a 22% increase in the second year. The first year witnesses an increase of 23 to 25 cm (9 to 10 inches) in height, but only half as much in the second. By the fifth year, weight increase is down to about 12%. However, boys continue a child-like growth for perhaps 2 longer years than the age at which the girls reach their growth peak at about puberty.
An infant’s body contains a much higher percentage of water than that of the older children and adults. Their muscles are poorly developed and the amount of subcutaneous fat is limited. Girls are 25% fatter than boys from birth. Weight gain by infants is generally about 38% fat between birth and six month of age, but only about 11% between six months and one year (an inverse relationship exists between fat and protein composition of weight gain at this age range). Since the skin surface area is high in proportion to the total body weight, the loss of body water and heat is relatively high.
Tissues are most vulnerable when their component cell numbers are increasing; and any disruption of this cell division may lead to a reduction in the basic cell population number. Any nutritional deficiencies during these periods (critical phases of growth) are highly significant and may be irremediable. Nutritional disruptions during periods when cell enlargement predominates are more readily reversible. At birth, the skeleton which is high in water content contains about 25 to 28 g of calcium, an amount which triples by the end of the first year.
The first requirement of a new-born is oxygen. Thus, its lungs must expand and its circulation begins to be re-routed. The next requirement is warmth, followed by food and water and the digestive organs have to come into operation. These organs have been developing from about the 4th week of gestation when the embryo weighs only a fraction of a gram and by term, are equipped with enzymes and are capable of digesting and absorbing the nutrients in the milk. Animal studies show that there is a vary rapid growth of all parts of the gastrointestinal tract in response to the first food after birth and it seems likely that a similar thing goes on in the human infants. The GI system of the full-term infant is able to digest proteins, emulsified fats and simple sugars (polymers of carbohydrates, glucose and even sucrose), but starches and most fats are poorly tolerated until some months later when the digestive system is fully developed. The kidneys reach their full functional capacity by the end of the first year. During the first few months, the glomerular filtration rate (GFR) is somewhat lower, and
excretion of high concentration of solutes is more difficult. Young infants excrete greater amounts of some amino acids on account of their lower ability to reabsorb them from the tubules.
Epidemiological findings however, show that solid or semi-solid foods ought to be part of the diet of the infant by the sixth month of age, even though there is little agreement as to the exact time when these become necessary. In the U.S., in the 1920s, solid foods were seldom given before one year of age. By 1963, 83% of infants between one and two months of age were eating them. Studies also indicate that full-term infants can tolerate cereals or cereal-based foods by the second or third day of life! There are no problems with vegetables at ten days, meat at 14 days, and fruits at 17 days! On account of the size of the stomach of the new-born, being about the size of its fist, the best food for the baby is undoubtedly the mother’s breast milk. Fortunately however, there is no need for any other type of food so early in life. In realistic or practical terms however, the amount of solids fed at first should be very little, and such solid food feeding in the first few months of life should be viewed only as a form of training for them to accept and swallow such foods. It will also sensitize their taste buds for others tastes besides the `sugary’, lactose-containing taste of the breast milk. Because this learning takes time, it is highly valuable and recommended that babies start on such weaning-taste exercise well before the six-month point of weaning. A delayed until the very sixth month of breast-feeding often leads to untold difficulties in weaning.
The hemoglobin level of the full-term infant at birth is about 17 to 20 g per 100 ml. The level gradually lowers as the infant grows and the blood circulation expands. The level remains satisfactory until the third month when iron-rich foods should be introduced.
The brain develops rapidly such that it completes its growth earlier than the rest of the body. By four years, its growth is 80 to 90% complete and 95% by ten years. The increase in the number of brain cells is most rapid during fetal life and in the first five to six months after birth. Severe malnutrition at any of these times leads to a reduction in the number of brain cells, with intellectual consequences in later life. These growth processes are controlled by a number of factors including genetic, hormonal as well as environmental or extrinsic factors. Among the extrinsic factors, nutrition is perhaps the most important.
Average Daily Requirements or Recommended Dietary Allowances (RDA) for Normal Infants and Young Children for Selected Nutrients**
Source National Open University of Nigeria