What is the adequate daily weight gain for premature infants?

Adequate Daily Weight Gain for Premature Infants

Premature infants should achieve a target weight gain of 17-20 g/kg/day after initial postnatal weight loss to prevent growth failure and support optimal neurodevelopmental outcomes. 1, 2

Understanding the Growth Trajectory

Initial Weight Loss Phase

• Premature infants typically experience postnatal weight loss in the first 2-3 days of life, with the weight nadir occurring around days 2-3 1
• This initial weight loss is physiologic and expected 1
• The target weight gain of 17-20 g/kg/day applies after this initial weight loss period, not from birth 1, 3

Why Growth Calculation Matters

A critical pitfall is calculating growth from birth versus from the weight nadir (dip). When growth is measured from birth, only 14% of premature infants meet growth targets, but when measured from the dip onward, 78% achieve adequate growth 3. This distinction is essential for accurate assessment and avoiding unnecessary interventions.

Nutritional Requirements to Achieve Target Growth

Energy Intake

• Target: 90-120 kcal/kg/day via parenteral nutrition to approximate intrauterine lean body mass accretion 1, 2
• Most practitioners aim for at least 120 kcal/kg/day to facilitate maximal protein accretion during catch-up growth 2
• Energy targets are often not met before day 5 of life, which can impact early growth 3

Protein Intake

• Start amino acids on day 1 at minimum 1.5 g/kg/day to achieve an anabolic state 2
• Advance to 2.5-3.5 g/kg/day from postnatal day 2 onwards as the evidence-based target range 2
• Protein delivery must be accompanied by adequate non-protein energy (>65 kcal/kg/day) to optimize protein utilization 2

Lipid Intake

• Start intravenous lipid emulsions immediately after birth or no later than postnatal day 2 2
• Advance to 3-4 g/kg/day in preterm infants 2

Clinical Application and Monitoring

When Growth Is Inadequate

Weight gain below 9 g/kg/day requires immediate intervention to prevent impaired neurodevelopment and long-term morbidity 1, 4. This represents less than half the target rate and signals significant nutritional inadequacy.

Intervention Strategy

• Initiate higher caloric intake of approximately 120 kcal/kg/day to promote catch-up weight gain 4
• For infants with chronic conditions, caloric needs may increase to 150 kcal/kg/day or more 4
• Schedule weight checks within 48-72 hours after initiating interventions to assess response 1

Evidence Quality Considerations

The 17-20 g/kg/day target is endorsed by both the American Academy of Pediatrics and the European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) 1, 2. However, research demonstrates that extrauterine growth restriction remains high (75% at 28 days) even when infants achieve growth velocity within current guidelines 5. This suggests that rates in the upper range (20-30 g/kg/day) may be necessary for the gestationally youngest infants to maintain their birth weight z-score 5.

Common Pitfalls to Avoid

• Do not calculate growth from birth weight alone - use the weight nadir as the starting point for growth assessment 3
• Do not delay nutritional intervention - early (day 7) nutritional practices are positively associated with growth velocity measured between days 7-28 5
• Do not underestimate protein needs - aggressive early nutrition improves outcomes 2
• Ensure adequate non-protein energy when providing high protein doses (>65 kcal/kg/day) to optimize nitrogen retention 2