Feeding Of Low Birth Weight Neonates

Newborn nutrition is a vital part of the well-being of an infant. The period of rapid growth in infancy requires careful nutritional support to continue the growth and development that began at conception. The main objectives in feeding infants are meeting nutritional needs, preventing nutritional deficiencies and promoting growth (1). Moreover recent evidence suggests that early nutrition has biological effects on the individual with important implications for later health.

Low birth weight infant (LBW) is one who weighs less than 2500 grams at birth. Every year 20 million low birth weight infants are born in the developing world and 40% of these are born in India. LBW infants are a heterogeneous group and would consist of preterm infants born <37 weeks of gestation and weighing less than 2500 gms as well as full term infants
if they weigh less than 2500 grams and the feeding guidelines would vary from one group to the other.

Feeding principles for full term LBW infants:

Human milk is the recommended nutritional source for full-term infants for at least the first six months of postnatal life (54th WHA).The advantages of breast feeding are not limited to childhood period but extend much beyond in adulthood as well.

1. Reduction of infection (Diarrhea, Acute respiratory tract infections, Otitis Medi Necrotizing Enterocolitis, Late onset sepsis)
2. Protection against allergies: less chance of eczema, milk allergy and asthma
3. Reduction of obesity / Diastolic blood pressure by 2mmHg /Type II DM / Leukemia / Breast cancer
4. Better cognition
5. Saves money / social issues
6. Reduction of under five child mortality by 13-15% in India
7. Maternal benefits

Knowing so many benefits to exclusive breastfeeding, it is strongly being emphasized by all agencies (WHO, AAP, IAP) to promote breast feeding till 6 months but the exclusive breast feeding rates in our country according to latest NFHS III is 46% which is low from all standards. Understanding that the incidence of true lactation failure is only 1%, there are other problems which can be sorted out by various practical solutions apart from increasing awareness: 

1. Establishment of Antenatal clinic for breast feeding promotion / Nipple examination by obstetricians or pediatricians or any health care worker.
2. Feeding in first hour of life to be emphasized which has been incorporated as essential part of Newborn Resuscitation Program and Kangaroo Mother Care.
3. Employment of lactation nurses/ Counselors in hospitals to help the mothers in actually initiating and maintaining lactation.
4. Special emphasis to babies born to LSCS mothers like pain management / different positions/ bedding in/ incision line care etc.
5. Promotion of breast milk expression techniques (by manual techniques or breast pumps) would help preterm babies, working mothers or if mother and baby is separated because of any reason.

After breastfeeding, the second best option for milk in first one year of life is infant term milk formula with composition as close to mothers milk as possible. But the commonest milk consumed by Indian infants is cow’s or buffalo’s milk which is definitely with lots of side effects namely iron deficiency anemia, Vitamin C/D deficiency disorders, increased risk of infections, increased renal solute load to kidneys especially important during acute diarrhea episodes and most important lack of DHA in bovine milk which is of paramount importance for brain and retina growth. Because of these serious limitations American Academy of Pediatrics recommends against use of cow’s milk till one year of age (2, 3). Pediatric academies of Canada, Scotland and UK recommend not using cow’s milk till 9 months of age. The age cut off of 9-12 months is based on the demonstration of microscopic bleeding from intestines in infants fed unmodified bovine milk till this age.

Supplementation of exclusively breast fed infants:

Because of widespread prevalence of Vit D deficiency disorders in infants, AAP guidelines (4) suggest to start Vit D (400IU/d) even in exclusively breast fed infants. Though there are concerns regarding exposure of infants to sunlight and later developments of skin cancer in white races; we don’t have any Indian figures to support or negate these observations and as of now we do recommend sun exposure for Vit D sufficiency. Iron supplementation is started at 6 months of age as later supplementation has been associated with increased prevalence of iron deficiency states whereas earlier supplementation is also not without risks of infection (especially in malaria endemic zones) and poor growth.

Feeding principles for preterm LBW infants

This group can be subdivided in two smaller groups:

1. Infants between 32 weeks and <37 weeks; 1800 gms to <2500 gms
2. Infants < 32 weeks and <1800 gms

The group no. 1 should be on the same feeding principles as that of full term infants in most situations and should be on direct breast feeds. The special need of nutrition (ESPGHAN) comes for the second group. European society of pediatric gastroenterology, hepatology ESPGHAN and nutrition has given its recommendations for this group which is at a distinct disadvantage because of various physiological limitations (5).

Very high growth rate

• Intrauterine weight gain 16-17 g/kg body weight per day (approx. 3 folds from 28th to 40th week)
• Gains around 20 cm in length
• Brain size increases three and half times

Very low nutrient stores

• Low fat & glycogen stores
• Lack of body building nutrients
• From 25th to 40th wk body accumulates 20,000 mg of calcium

Immature organs

GI tract:

• Increased GI tract permeability leading to intestinal inflammation and injury
• Delayed gut colonization with Bifidobacteria
• From 25th to 40th wk body accumulates 20,000 mg of calcium

Lack of Digestion & Absorption:

• Smaller stomach capacity
• Delayed emptying of gastric content
• Low levels of intestinal lactase, lactose digestion is poor
• Low levels of pancreatic lipase and bile salts results in poor Fat absorption

Renal Function:

• Low glomerular filtration rate
• Acidosis occurs early
• Low levels of intestinal lactase, lactose digestion is poor
• Poor Urine concentration. Infant gets dehydrated readily

Central Nervous System:

• Uncoordinated sucking and swallowing
• Regurgitation & aspiration

Respiratory system:

• Resuscitation problems
• Hyaline membrane disease
• Vulnerable to chronic pulmonary insufficiency due to bronchopulmonary dysplasi

The current concept of nutrition of very low birth weight infants is to provide aggressive nutrition as the ill effects of under nutrition are well established. During the acute phase of the disease, aim is to avoid catabolism and not growth. This is difficult in VLBW infants due to higher requirements, poor stores and reduced intake. After stabilization during the growing period, aim is to approximate in utero growth rate of a normal fetus of the same gestation with no functional impairment. There should be positive energy balance to sustain growth. Inadequate Nutrition leads to poor post natal growth which ultimately leads to impaired neurocognitive development.

Sources of nutrient recommendations for preterm infants include the American Academy of Pediatrics Committee on nutrition, the European Society of Paediatric Gastroenterology and Nutrition Committee on Nutrition (ESPGAN-CON), National Neonatology Forum (NNF) (6) and the reasonable ranges of nutrient intakes published by Tsang et al (7).

Choice of milk for feeding preterm babies:

The different choices of milk for preterm are Breast milk, Fortified human milk, Preterm specialized formula milk.
Breast milk remains the choice of feeding of all neonates. Breast milk confers significant advantage for protection against infection and NEC in preterm infants. Breast milk in sufficient volume has been shown to achieve a desirable weight gain in preterm infants. Breast milk provides ideal whey casein ratio (60:40) and whey protein is easily digestible, contains long chain polyunsaturated fatty acid (LCPUFA) which is important for brain and retinal growth, contains oligosaccharides which helps in host defense. The neurodevelopmental outcome also has been reported to be better with breast feeding. However feeding exclusive breast milk to a preterm baby <32 weeks may have certain disadvantages. Though preterm milk initially contains higher protein but the protein content gradually declines over next 3–4 postnatal weeks. It also contains inadequate amounts of calcium and phosphate. A growing preterm needs higher protein, calorie, calcium, phosphate than what can be provided by breast milk alone. Hence, the preterm babies may need additional supplements during the catch up growth if weight gain is not adequate. Table1 shows recommended nutrient intakes as per ESPGHAN 2009

Nutritional requirements of preterm infants for some important nutrients (5):
Energy: Recommendations for energy intake are based on growth and nutrient retention similar to intrauterine references. The recommendations should achieve not only weight gain but also body composition similar to intrauterine growth standards. It is also emphasized that rapid infant weight gain in term infants may be associated with adverse outcomes. Synthesis of new tissue is strongly affected by the intake of protein and other nutrients; thus, achieving an adequate energy to protein ratio is as important as providing adequate energy intake. Based on intrauterine standards, a reasonable range of energy intake fo healthy growing preterm infants with adequate protein intake is 110 to 135 kcal/kg/day. Increasing energy intake may not be appropriate for infants whose growth appears inadequate (without evidence of fat malabsorption) because it is more likely that other nutrients (eg, protein) are rate limiting.

Proteins: Proteins are the main building blocks and a suboptimal intake of protein, energy, and other nutrients may lead to lower cognitive achievements. Protein accretion has been estimated at approximately 1.7 gm/ kg/day for fetuses throughout the second half of gestation but is lower at the end of gestation. Obligatory protein losses are at least 0.7 gm/kg/day but may be higher if nitrogen losses from skin and breath could be measured. Based on the protein needs and nitrogen utilization, the protein intake should be at least 3.0 gm/kg/day. Intrauterine weight gain can be matched at protein intakes <32 3 to 3.5 gm/kg/day accompanied by a high energy intake, but body fat percentage will then be much higher than observed in the foetus. Intakes in the range of 3 to 4.5 gm/kg/day will achieve acceptable plasma albumin and transthyretin concentrations. Some excess of protein intake over requirements was not shown to cause detrimental effects in preterms, but a small deficit will impair growth. ESPGHAN recommends 4.0 to 4.5 gm/kg/day protein intake for infants up to 1000 g, and 3.5 to 4.0 gm/kg/day for infants from 1000 to 1800g, this will meet the needs of most preterm infants.

Lipids: Apart from providing much of its energy needs, dietary lipids also provide the preterm infants with essential polyunsaturated fatty acids, and lipid-soluble vitamins. Long chain polyunsaturated fatty acids (LCPUFA) are important for cell membrane functions and the formation of bioactive eicosanoids. Brain grey matter and the retina are particularly rich in long-chain polyunsaturated fatty acids.
Assuming a daily intrauterine fat deposition of 3 g/kg, 10% to 40% loss from fat malabsorption, and 15% loss from unavoidable oxidation, and conversion of absorbed triglyceride to deposited triglyceride in tissue, a minimal dietary fat intake of 4.8 gm/kg/day is suggested. Although some infants with restricted fluid and feed intakes may need high fat intakes to meet energy needs, for most preterm infants a reasonable range of fat intake is 4.8 to 6.6 gm/kg/day or 4.4 to 6.0 g/100 kcal (40–55 % of energy intake). The medium-chain triglyceride content in preterm formulae, if added, should be in the range of up to 40% of the total fat content. The recommended intakes are for DHA(docosahexaenoic acid) 12-30 mg/kg/day and for AA (arachidonic acid) 18-42 mg/kg/day with a ratio of AA: DHA 1-2:1. Eicosapentaenoic acid competes with AA and the levels are low in human milk; hence its supply should not exceed 30% of DHA supply.

Calcium: Calcium absorption depends on calcium and vitamin D intakes, and that calcium retention is additionally related to absorbed phosphorus. Various studies suggest that calcium retention ranging between 60 to 90 mg/kg/day decreases the risk of fractures, diminishes the clinical symptoms of osteopenia, and ensures appropriate mineralisation in very-lowbirth- weight (VLBW) infants. Thus, a calcium intake of 120 to 140 mg/kg/day with an absorption rate of 50% to 65% will lead to calcium retention of 60 to 90 mg/kg/day.

Phosphorus and Calcium to Phosphorus ratio: The calcium to phosphorus ratio may be an important determinant of calcium absorption and retention. The present recommendation for preterm formula is calcium to phosphorus ratio close to 2:1, but ideally this should be adapted taking into account nitrogen retention as well as bioavailability of the calcium salt. Considering a nitrogen retention ranging from 350 to 450 mg/kg/day and calcium retention from 60 to 90 mg/kg/day, the adequate phosphorus intake represents 65 to 90 mg/kg/day of a highly absorbable phosphate source (90%) with a calcium to phosphorus ratio between 1.5 and 2.0. Individual needs can be determined by measuring spot urinary calcium < 6mg/kg/d and Urinary excretion of P>4mg/kg/d.

Vitamin D: Vitamin D is important for supporting a large number of physiological processes such as neuromuscular function and bone mineralization. The requirements of Vitamin D for optimal growth in VLBW and extremely-low-birth-weight infants are still matters for discussion. Studies have suggested a vitamin D intake of 800 to 1500 IU/day which is necessary to reach a circulating 25(OH)D concentration above 75 nmol/L. ESPGHAN recommends a vitamin D intake of 800 to 1000 IU/day (and not per kilogram) during the first months of life.

Iron: Iron is essential for brain development, and many observational studies have shown an association between iron deficiency anemia and poor neurodevelopment in infants. Excessive iron supplementation of infants on the other hand may lead to increased risk of infection, poor growth, and disturbed absorption or metabolism of other minerals. Thus one must prevent not only iron deficiency but also iron overload.
ESPGHAN recommends an iron intake of 2 to 3 mg/kg/day, given as a separate iron supplment, in preterm formula or in fortified human milk. Iron supplementation should be started at 2 to 6 weeks of age (2–4 weeks in extremely low birth weight infants). Infants who receive erythropoietin treatment and infants who have had significant, uncompensated blood losses may initially need a higher dose, requiring a separate iron supplement in addition to preterm formula or fortified human milk. Enteral iron doses >5mg/kg/day should be avoided in preterm infants because of the possible risk of retinopathy of prematurity. Iron supplementation should be delayed in infants who have received multiple blood transfusions and have high serum ferritin concentrations. Iron supplementation should be continued after discharge, at least until 6 to 12 months of age depending on diet.

Table 2 showing composition of various feeding options available for preterm infants per 100 ml of feed.

Which milk is the best milk for preterms?

As evident from the above discussion, there are certain increased requirements for these preterm neonates and hence fortified human milk is the best available option to meet the nutritional requirements of preterm babies. Alternatively a preterm formulae would be required for this group of preterm neonates.

Feeding protocol for preterm babies, < 32 weeks and < 1800 grams: 
Choice of milk:

First choice milk is Maternal EBM (with HMF supplementation to 24 calories/30mls when the baby is tolerating 100mls/kg/day). Second choice milk would be Preterm formula.
Initiation of feeding:

• Well babies
  • > 30 weeks can be started immediately on total milk feeds
  • <30 weeks: start feeds on D1 along with parenteral nutrition
  • < 28 weeks : minimal enteral feeds on Day 2 or 3
    
• Sick babies
  • > 28 weeks, start enteral feeds when it is felt clinically appropriate

Progression of feeds:

• Well baby, no risk factors, baby tolerating feeds: Increase by 20 – 30 ml/kg/day
• Slow progression if baby shows features of feed intolerance
• In defining the rate of increase the following need to be considered
  • Gestation and weight of the baby.
  • How sick the baby has been.
  • How well the milk is being tolerated (vomits or large residuals)
  • Any abdominal signs eg. distension.

Final feed volume:

Final feed needs to be individualized in each baby. A weight gain 15g/kg/day (range 10-25g/kg/day) should be targeted which can be achieved at a volume of around 180 ml/kg/day.

Nutritional assessment of the Enterally fed premature infant

A daily weight gain of 1 – 1.5% of birth weight, Length gain of approx 0.9cm / week and increase in head circumference of 0.7 – 0.9 cm/week are ideal desired targets

Post discharge feeding:

Most of the follow up studies of VLBW and ELBW show that at discharge they are <10th centile and this growth failure continues in next few years. Though the current feeding policies concentrate only on feeding practices during hospital stay, there is a need to have adequate calorie, protein and other mineral intake after discharge also. Policy of aggressive nutrition for preterm VLBW and ELBW infants should continue beyond discharge to improve growth during early infancy and childhood.

Practical guidelines at discharge:

• For babies on direct human milk: continue calcium/phosphorus, iron and multivitamin drops and follow up on the growth chart. If continue to follow the target percentile; continue. If percentile starts falling, add HMF.
• For babies on human milk but not direct feeds: < 1800gms - discharged on HMF, MV drops/ iron. Calcium/phosphorus supplementation not required.
• Alternative is preterm special formulae

Growth charting:

These babies should be followed on intrauterine growth charts (e.g. Modified Fenton’s charts 2013) till 40 weeks of gestation and then subsequently on WHO growth standard charts.

Conclusion:

There is ample evidence that most of the VLBW and ELBW infants suffer significant postnatal malnutrition (extrauterine growth restriction) and become <10 th percentile for weight at discharge. Hence one should adopt the policy of aggressive enteral nutrition from very early in life. As parenteral nutrition has its own complications and is expensive, one should attempt oral feeding as soon as the baby is stable. For high risk babies at least minimal enteral nutrition (18-24 ml/kg/day) should continue till the baby is ready for full feeds. Breast milk should be fortified with Human milk fortifier for babies <1800gms. Even breast fed babies should get additional supplements with minerals, vitamins and iron which should continue even after discharge. Alternatively preterm babies should get preterm term formula till 40 weeks or till they reach their birth percentile.

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