Growth Monitoring in Preterm Infants: Fenton Charts, Corrected Age, and Nutritional Optimization

Summary

• Use the 2025 Fenton third-generation growth charts for preterm infants until 50 weeks postmenstrual age (PMA), then transition to WHO growth standards [2,3,4].
• Apply corrected age to all growth and developmental assessments through at least 24 months, and through 36 months for accurate growth classification [7].
• Weight gain of 15-20 g/kg/day is an appropriate target only for 23-36 weeks PMA; targets shift with age, and both under- (<10 g/kg/day) and over-gain (>25 g/kg/day, fluid overload) carry clinical meaning [8].
• Enteral protein target is 3.5-4.5 g/kg/day, higher in infants <1000 g (4-4.5 g/kg/day) than in those 1000-1500 g (3.5-4 g/kg/day) [10,22].
• Fortify human milk for all VLBW infants; unfortified milk provides only about 67 kcal/100 mL and 1.1 g/100 mL protein, below VLBW requirements [14].
• Growth chart choice affects both classification and prognostic value: Fenton-defined poor weight gain predicts 18-month Mental Developmental Index <85 (aOR 1.6, 95% CI 1.1-2.4); INTERGROWTH-21st-defined poor weight gain does not (aOR 1.0, 95% CI 0.6-1.7) [6].

Growth Charts

The Fenton third-generation preterm growth charts (2025) update the prior version using a systematic review and meta-analysis of 4.8 million births from 15 countries, including 174,184 infants born at less than 30 weeks' gestation [2,3].

Changes from prior versions:

• Exclusion of infants with abnormal fetal growth. The charts are derived from preterm infants without intrauterine growth restriction, giving a true growth standard rather than a reference that includes pathologic growth [2,3].
• Improved growth velocity consistency. Slopes are more uniform across percentiles and align more closely with fetal ultrasound estimates [2,3].
• Rescaled x-axis. Charts now use exact gestational age in weeks and days rather than completed weeks [2,3].

The AAP recommends the Fenton chart until 50 weeks PMA; after that point, percentiles match WHO growth standards [4].

Open the Fenton Preterm Growth Chart →

During hospitalization, plot measurements by PMA, not corrected age.

Clinical pearl. A 30-week gestation infant at 34 weeks PMA is plotted at 34 weeks. This reveals whether the infant is tracking the expected curve or deviating from the expected trajectory.

Growth Chart Selection: Fenton vs. INTERGROWTH-21st

A 2026 comparison found that chart selection changes how preterm infants are classified [5]:

Caution. Poor growth classified using fetal references (Fenton, Olsen) shows a stronger association with long-term neurodevelopment than poor growth classified using INTERGROWTH-21st [6]. Chart choice is not interchangeable when growth status is being used to flag neurodevelopmental risk.

Corrected Age

The AAP recommends corrected age for all growth and developmental assessments until 24 months corrected age. After 50 weeks PMA, transition to WHO growth standards plotted with corrected age.

A 2025 study of 1,416 extremely and very preterm children found that age correction is required through at least 36 months corrected age for accurate growth assessment [7]. Using chronologic age instead of corrected age produced:

• Weight z-scores up to 5.2 lower than corrected age-based scores at term
• Up to 72.9% of children misclassified as stunted and 89.8% misdiagnosed as underweight at term
• Persistent misclassification through 36 months of age

Formula: Corrected age = Chronologic age − (40 weeks − Gestational age at birth)

Calculate corrected age →

Clinical pearl. A 6-month-old infant born at 28 weeks gestation has a corrected age of approximately 3 months (6 months − 3 months prematurity = 3 months corrected age).

Growth Velocity

Targets are age-dependent and must be interpreted against PMA rather than applied as flat rules [8].

Weight gain

• 15-20 g/kg/day is a reasonable goal for 23-36 weeks PMA (average or exponential calculation methods)
• The commonly cited "15 g/kg/day" fits current growth references only for a limited window; rates are higher before 34 weeks and lower after
• <10 g/kg/day indicates inadequate nutritional support
• \>25 g/kg/day raises concern for fluid overload

Length velocity

• 1 cm/week fits growth references for approximately 37-40 weeks PMA
• Suboptimal length velocity is associated with neurodevelopmental problems

Head circumference

• 1 cm/week fits growth references for approximately 23-30 weeks PMA
• Inadequate head growth is associated with impaired neurodevelopment and poor cognitive outcomes

Post-discharge growth velocity [4]

Nutritional Requirements

Protein [10,22]

Protein intake of 3-4 g/kg/day promotes weight gain and nitrogen accretion [10].

Energy

• 110-135 kcal/kg/day for hospitalized VLBW infants [11,22]
• 100-120 kcal/kg/day post-discharge, targeting weight gain of at least 20-30 g/day [4]

Calculate glucose infusion rate → Open the Neonatal TPN Calculator →

Use the GIR calculator when managing parenteral nutrition to optimize glucose infusion and avoid hyperglycemia. Use the TPN calculator to individualize macronutrient targets.

Human Milk Fortification

Human milk is the preferred nutrition source for preterm infants. It protects against sepsis and necrotizing enterocolitis (NEC) and is associated with improved neurodevelopmental outcomes [12]. Unfortified human milk provides only about 67 kcal/100 mL and 1.1 g/100 mL protein, insufficient for VLBW infants.

Fortification evidence [14]

Fortification approaches

1. Standard (fixed): fortifier added at a fixed dose to reach approximately 80 kcal/100 mL and 2 g protein/100 mL
2. Adjustable: blood urea nitrogen used as a surrogate for protein nutriture to titrate fortification
3. Targeted (individualized): based on periodic human milk analysis via point-of-care analyzers; an RCT showed improved growth with individualized versus standardized fortification [9]

Timing of fortification

• Several recent RCTs of fortification at feeding volumes <80 mL/kg/day showed no association with feeding intolerance or NEC [13]
• A 2023 RCT showed improved linear growth in infants <28 weeks who received fortification on day 2 versus day 14 [16]
• A 2025 RCT in very preterm infants found early fortification (days 4-7) produced higher weight (+131 g), higher fat-free mass (+103 g), and greater length (+0.9 cm) than delayed fortification (days 10-14) [17]

Mother's own milk vs. donor milk

• Mother's own milk (MOM) has higher protein content than term milk until about 10-12 weeks after birth
• Pasteurized donor human milk (PDHM) has significantly lower protein, sodium, chloride, potassium, and zinc content than preterm MOM [18]
• Infants supplemented with PDHM may have increased risk of slower growth even with fortification [18]
• MOM is nutritionally and biologically superior to PDHM, reinforcing the value of supporting maternal lactation [15]
• PDHM is recommended when MOM is unavailable. It reduces NEC risk compared with formula but does not confer MOM's additional benefits, including reduced late-onset sepsis and improved neurodevelopment [15]

Neurodevelopmental Outcomes

Head circumference

• Inadequate head growth is associated with impaired neurodevelopment and poor cognitive outcomes
• A 1-unit increase in HC z-score from birth to 18-24 months corrected age is associated with lower odds of significant cognitive/motor impairment (OR 0.81, 95% CI 0.75-0.88) [20]

Weight gain

• A 1 g/day increase in weight from discharge to 18-24 months corrected age is associated with lower odds of significant cognitive/motor impairment (OR 0.87, 95% CI 0.83-0.91) [20]

Growth restriction

• SGA infants without catch-up growth have unfavorable neurodevelopmental outcomes (IQ β −6.5, 95% CI −9.8 to −3.2) [19]
• SGA infants with catch-up growth are comparable to adequately grown infants [19]
• Achieving adequate early-life growth may be critical for optimizing neurodevelopmental outcomes

Post-Discharge Management

Growth expectations

• Healthy preterm infants typically achieve growth catch-up by 12-24 months corrected age
• SGA infants at birth show slower catch-up growth and lower bone mass accumulation than AGA infants
• Failure to achieve catch-up by 36 months is associated with suboptimal neurodevelopmental outcomes

Nutritional guidance

• Continue fortified breast milk or nutrient-enriched formula until catch-up growth is achieved
• Post-discharge caloric target: 100-120 kcal/kg/day for weight gain of at least 20-30 g/day
• Dietary advancement should track neurodevelopmental milestones, not chronologic age alone

Caution. Once catch-up growth is achieved, discontinue fortification. Continued fortification past this point risks hypervitaminosis, obesity, and hypertension.

Follow-up schedule [21]

• Early post-discharge follow-up within 1-2 weeks
• Confirm families and primary care providers understand corrected age application
• Continue corrected age for all assessments through 24-36 months
• Standardized developmental screening, adjusted for corrected age, is particularly important in infants at higher risk of developmental delay

References

1. Inder TE, Volpe JJ, Anderson PJ. Defining the Neurologic Consequences of Preterm Birth. N Engl J Med. 2023;389(5):441-453.
2. Fenton TR, Elmrayed S, Alshaikh BN. Fenton Third-Generation Growth Charts of Preterm Infants Without Abnormal Fetal Growth: A Systematic Review and Meta-Analysis. Paediatr Perinat Epidemiol. 2025.
3. Fenton TR, Elmrayed S, Alshaikh BN. Fenton Third-Generation Growth Charts of Preterm Infants Without Abnormal Fetal Growth: A Systematic Review and Meta-Analysis. Paediatr Perinat Epidemiol. 2025;39(6):543-555.
4. Bybel M, Delaney CA, Coble K. Outpatient Care of the Premature Infant. Am Fam Physician. 2025;112(2):153-161.
5. Merino-Hernández A, Rodríguez-Corrales E, Ramos-Navarro C, et al. Fenton vs INTERGROWTH-21st Charts in Preterm Infants < 32 Weeks: Impact of Chart Selection on Growth Classification. Eur J Pediatr. 2026;185(2):114.
6. Cordova EG, Cherkerzian S, Bell K, et al. Association of Poor Postnatal Growth With Neurodevelopmental Impairment in Infancy and Childhood: Comparing the Fetus and the Healthy Preterm Infant References. J Pediatr. 2020;225:37-43.e5.
7. Elmrayed S, Dai S, Lodha A, Kumar M, Fenton TR. Preterm Growth Assessment: The Latest Findings on Age Correction. J Perinatol. 2025;45(5):607-615.
8. Fenton TR, Anderson D, Groh-Wargo S, et al. An Attempt to Standardize the Calculation of Growth Velocity of Preterm Infants, Evaluation of Practical Bedside Methods. J Pediatr. 2018;196:77-83.
9. Fabrizio V, Trzaski JM, Brownell EA, et al. Individualized Versus Standard Diet Fortification for Growth and Development in Preterm Infants Receiving Human Milk. Cochrane Database Syst Rev. 2020;11:CD013465.
10. Fenton TR, Al-Wassia H, Premji SS, Sauve RS. Higher Versus Lower Protein Intake in Formula-Fed Low Birth Weight Infants. Cochrane Database Syst Rev. 2020;6:CD003959.
11. Abiramalatha T, Thomas N, Thanigainathan S. High Versus Standard Volume Enteral Feeds to Promote Growth in Preterm or Low Birth Weight Infants. Cochrane Database Syst Rev. 2021;3:CD012413.
12. Meek JY, Noble L. Technical Report: Breastfeeding and the Use of Human Milk. Pediatrics. 2022;150(1):e2022057989.
13. Thanigainathan S, Abiramalatha T. Early Fortification of Human Milk Versus Late Fortification to Promote Growth in Preterm Infants. Cochrane Database Syst Rev. 2020;7:CD013392.
14. Brown JV, Lin L, Embleton ND, Harding JE, McGuire W. Multi-Nutrient Fortification of Human Milk for Preterm Infants. Cochrane Database Syst Rev. 2020;6:CD000343.
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17. Salas AA, Gunawan E, Jeffcoat S, Nguyen K. Early Full Enteral Nutrition With Fortified Milk in Very Preterm Infants: A Randomized Clinical Trial. Am J Clin Nutr. 2025;121(5):1117-1123.
18. Gates A, Hair AB, Salas AA, Thompson AB, Stansfield BK. Nutrient Composition of Donor Human Milk and Comparisons to Preterm Human Milk. J Nutr. 2023;153(9):2622-2630.
19. Ruys CA, Hollanders JJ, Bröring T, et al. Early-Life Growth of Preterm Infants and Its Impact on Neurodevelopment. Pediatr Res. 2019;85(3):283-292.
20. Bando N, Fenton TR, Yang J, et al. Association of Postnatal Growth Changes and Neurodevelopmental Outcomes in Preterm Neonates of <29 Weeks' Gestation. J Pediatr. 2023;256:63-69.e2.
21. Davis BE, Leppert MO, German K, Lehmann CU, Adams-Chapman I. Primary Care Framework to Monitor Preterm Infants for Neurodevelopmental Outcomes in Early Childhood. Pediatrics. 2023;152(1):e2023062511.
22. Embleton ND, Moltu SJ, Lapillonne A, et al. Enteral Nutrition in Preterm Infants (2022): A Position Paper From the ESPGHAN Committee on Nutrition. J Pediatr Gastroenterol Nutr. 2023;76(2):248-268.