Nutrition for Premature Babies

What is known and what is unknown? What is different about nutrition for a premature baby compared to a term baby? What would you need to prepare yourself for, if your baby was born premature?
By Dr Yvonne Ng Peng Mei, Neonatologist with the University Children’s Medical Institute at the National University Hospital

Premature babies are babies born before full term gestation of 37 completed weeks of pregnancy. Out of 100 babies born, about 7 babies will be born prematurely. Premature babies can be as immature as 24 weeks (mean weight 700 grams) or as mature as 35 weeks (mean weight 2.5 kg). Premature babies can also be classified according to birth weight: Very Low Birth Weight (VLBW) babies weigh less than 1500g at birth.

There are multiple challenges to being born early. Premature babies’ organ systems are immature, they need to grow and develop outside the womb, supported by nutrition that the neonatologist and the mother provide.

Desired nutritional outcomes for the premature baby

What are goals of nutrition for the premature baby? The ultimate goal is for the premature infant to grow like a normal fetus. Nutrients need to be provided to meet the rate of growth and body composition of a normal fetus. For a simple way of visualising this, please refer to the Fenton Chart. A premature baby born at 30 weeks who weighs 1.5kg is at the 50th percentile, his weight at 6 weeks old or 36 weeks ideally should be close to the 50th percentile (2.8kg). Another way of targeting growth is to aim for fetal growth rate in the third trimester of pregnancy of 15 g/kg per day.

However, the premature baby starts off with a nutritional deficit soon after leaving the ‘comfort’ of the womb. Premature babies lose 10 to 15% of their birth weight in the first week of life, as a natural process, and regain their birth weight at about 2 weeks old. In premature infants, nutrient intakes often fail to meet the recommended dietary intakes in early weeks of life, especially during episodes of illness or when premature infants do not digest their milk feeds well.

Therefore, in practice, it is difficult to maintain the high rate of growth in the womb after baby is born. Additionally, optimal rates of growth may still be ill-defined and laden with controversies. Slow weight gain in the Neonatal Intensive Care Unit (NICU) delays time to discharge home, poor brain growth may increase risks of developmental problems in early childhood. However, what is not known is the effect of over-rapid growth on long-term health. Barker’s hypothesis proposes that malnutrition in fetal and early life results in metabolic adjustments, increasing risks of metabolic disorders in later life (adult onset diabetes, hypertension and cardiovascular disease) if the infant experiences over-nutrition and excessive growth. So, while it may be good to have catch-up growth, too much of a good thing is not good.

Feeding considerations for the preterm baby

If you need to choose to feed your preterm baby anything to make him or her grow healthy and smart, what would it be? There are no controversies in this matter, nor there really need to be a choice. Breast milk is still the best milk for the preterm baby. Advantages of human milk for nutrition include improved gastrointestinal function, digestion, and absorption of nutrients for the immature intestinal system. Many factors in breast milk play important roles in protection against infection, brain and eye development and cell growth. For a mother who has delivered prematurely, being able to nourish her infant with her breast milk enhances her psychological well-being.

Current practices in the NICU

Over the years, neonatologists are more aware of the need to provide optimum nutrition for preterm babies to avoid growth failure. A two-prong approach is to start early milk feeds as well as provide adequate calories and nutrients delivered directly into the blood stream (parenteral nutrition). Once milk feeds are established, mother’s breast milk is usually fortified with commercially available fortifiers to increase amounts of calories, protein, minerals, and vitamins for improved growth and development, as recommended by the European Society for Paediatric Gastroenterology, Hepatology, and Nutrition Committee on Nutrition.

Before NICU discharge, a feeding plan is developed with the parents. The goal is to maintain breast milk feeding with a targeted weight gain of at least 15 g/kg per day or higher. For breast-milk fed preterm infants who do not maintain adequate growth, an approach may be to provide a few feeds daily of a post-discharge enriched formulas (for increased intake of protein and calories) or continue fortification of breast milk at home. The infant’s growth will be monitored (weight, length, head circumference) with feeding plans reviewed and individualised at follow up visits.

In summary, mother’s milk is the preferred nutrition, with nutrient fortification for most VLBW infants, until at least the time of hospital discharge. Some amount of catch up growth is desired but excessive growth should be avoided. Nutritional goals should be optimised and individualised for each premature infant.

The Fenton Chart is used to plot a premature infant growth (weight, length, head circumference) longitudinally from the time of birth till infant reaches the corrected age of

10 weeks (50 weeks equals full term of 40 weeks plus 10 weeks). The infant’s growth falls on percentile lines (3rd, 10th etc) based on a reference population.