Adequate Weight Gain for Preterm Infants
For very low birth weight preterm infants, aim for a weight gain of 17-20 g/kg per day after the initial postnatal weight loss to match intrauterine growth rates and prevent growth failure. 1
Weight Gain Targets by Phase
Initial Postnatal Period (First Week)
- Expect physiological weight loss in the first 4-7 days
- Weight loss ranges from 4-13% depending on birth weight (lower birth weight = greater percentage loss) 2, 3
- Birth weight should be regained by 15-23 days of life, with smaller infants taking longer 2, 3
Growth Phase (After Regaining Birth Weight)
Primary Target: 17-20 g/kg/day is the recommended weight gain velocity for very low birth weight infants 1. This target:
- Approximates intrauterine growth rates
- Prevents dropping across weight centiles (growth failure)
- Represents a strong recommendation with strong consensus from ESPGHAN/ESPEN/ESPR/CSPEN 2018 guidelines
Alternative Expressions of Weight Gain
The evidence shows weight gain can be expressed differently:
- Absolute weight gain: 15-30 g/day (varies with birth weight - higher birth weight infants gain more absolute grams) 2
- Relative weight gain: Inversely proportional to birth weight when expressed as g/kg/day, with peak velocity around the 3rd week of life 2
Energy Requirements to Achieve Target Growth
To support the 17-20 g/kg/day weight gain target 1:
- Enteral feeding: 110-135 kcal/kg/day, with many practitioners targeting ≥120 kcal/kg/day to facilitate maximal protein accretion
- Parenteral nutrition: 90-120 kcal/kg/day (lower than enteral due to reduced splanchnic metabolism and stool losses)
- First day of life: Minimum 45-55 kcal/kg/day to meet basal energy requirements
Important Clinical Considerations
Gestational Age Matters
Research demonstrates that weight gain velocity of 17-18 g/kg/day occurs between 31-34 weeks gestation, decreasing to 4-5 g/kg/day by 50 weeks across all gestational age groups 4. The growth pattern remains consistent regardless of initial gestational age at birth.
Common Pitfalls to Avoid
Inadequate early nutrition: The guidelines emphasize that inadequate nutrient intakes are associated with impaired growth, increased severity of postnatal diseases, and adverse neurodevelopment, particularly in extremely preterm infants 1
Using inappropriate growth references: The 17-20 g/kg/day target is specifically designed to prevent infants from dropping across weight centiles on appropriate growth charts 1
Underestimating needs: Many clinical settings fail to achieve prescribed nutritional intakes, with actual intake sometimes 20% less than prescribed 1
Monitoring Strategy
Serial measurements of weight should be performed to ensure infants are achieving the target velocity. If the 17-20 g/kg/day target is not met, energy and protein intakes should be adjusted upward, ensuring adequate protein intake (typically requiring the higher end of energy recommendations at 120 kcal/kg/day for enteral feeds) 1.
The rationale for this aggressive approach is clear: early nutrition has critical short and long-term effects on morbidity and neurodevelopmental outcomes, making adequate postnatal growth a priority for optimizing quality of life in this vulnerable population 1.