Topic 4: Monitoring of nutrition and growth

Evidence-based recommendations for clinical practice around the monitoring of nutrition and growth for preterm babies.

On this page:

Question 49. What specific growth parameters (e.g., weight, length, head circumference, BMI) should be included in growth monitoring, and how frequently should they be monitored?

(NB These two questions have been combined into one recommendation)

Recommendation (adapted)

Measure weight, length and head circumference at least weekly. Use calibrated digital scales (to nearest 5 g) for weight, a neonatometer for length (to nearest mm) and non-stretch tape for head circumference. Apply Fenton 2025 growth charts from birth to 50 weeks postmenstrual age, then switch to WHO standards. Correct for gestational age up to 2 years.

[Strong recommendation]

Justification

Particularly important in very preterm or growth-restricted infants where early deviations have long-term consequences.

Subgroup considerations

Particularly important in very preterm or growth-restricted infants where early deviations have long-term consequences.

Implementation considerations

Units should ensure access to standard equipment and train staff in correct technique and use of growth charts.

Monitoring and evaluation

Audit compliance with measurement protocols and consistency in growth chart use.

Research priorities

  • Further research needed on the accuracy of growth tools in extreme prematurity and long-term outcomes based on early monitoring trends.

Question 50. What are acceptable growth goals for appropriate for gestational age (AGA) and small for gestational age (SGA) infants?

Recommendation (adopted)

Nutritional management and growth assessment for infants born with in-utero growth restriction and/or SGA should be the same as those born AGA, although initial weight loss is often less (up to 7% of birthweight is acceptable).

[Strong recommendation] 

Subgroup considerations

Extremely preterm and SGA infants may require nuanced plans based on clinical complexity.

Implementation considerations

Requires multidisciplinary input and education to avoid overtreatment. To calculate z-score, use the mobile phone application links below:

(iOS) NeoGrowth Fenton 2025

(Android) AnthroCalc

Monitoring and evaluation

Track longitudinal growth and ensure proportionality of weight and length gain.

Research priorities

  • More evidence needed on long-term outcomes of different SGA growth trajectories and the best nutrition practices.

Question 51. What is the definition of faltering growth that requires attention or nutritional intervention for preterm infants?

Recommendation

Assess after 2–3 weeks of age, and once birthweight is regained. Use these recommendations to screen for and intervene to resolve faltering growth:

Weight z-score change from birth

To calculate z-score, use the mobile phone application links below:

(iOS) NeoGrowth Fenton 2025 

(Android) AnthroCalc 

  • Infants with mild malnutrition (loss of >0.8 z-score) may require a higher feed volume/nutrient intake.
  • Infants with moderate malnutrition (loss of >1.2 z-score) should be referred to a neonatal dietitian for individual assessment of their growth and intervention if needed.

[Conditional recommendation]

Justification

Until there is a clearer definition of when nutritional intervention is required with faltering growth in preterm infants, it is reasonable to use international recommendations suggested by (Goldberg et al., 2018) to screen for and characterise faltering growth.

Subgroup considerations

ELBW infants may follow different growth trajectories and require earlier and more frequent monitoring. No specific evidence was found for Māori or Pacific infants, but systemic factors affecting growth (e.g. access to lactation support, early nutrition and hospital resource variation) must be considered when applying thresholds across populations.

Implementation considerations

Use serial growth monitoring using weight, length and head circumference z-scores with validated preterm growth charts (e.g. Fenton 2025). Train neonatal teams in interpreting growth trajectories and z-score changes.

Monitoring and evaluation

Monitor implementation through routine audit of adherence to the recommended screening criteria, documentation of growth assessment methods and appropriateness and timeliness of dietitian referral. Findings should be reviewed regularly to support quality improvement and consistent application across services.

Research priorities

  • What faltering growth criteria are associated with adverse outcomes in preterm infants?
  • Does screening for growth faltering in preterm infants reduce morbidity or adverse outcomes?

Question 52. Biochemical monitoring to monitor parenteral nutritional adequacy and tolerance. If, why and when should these be measured/monitored and for how long? What are the reference ranges for the neonatal population?

Sodium Triglycerides Ammonia 
Calcium Blood urea nitrogen Alkaline phosphatase
Phosphate Bicarbonate Parathyroid hormone
Magnesium Creatinine Liver function tests
Potassium Haemoglobin Trae elements
Blood gases Ferritin Fat-soluble vitamins
Blood glucose Full blood count (including reticulocytes) Urinary sodium and phosphate
Blood pH  Albumin and protein Urinary glucose

Recommendation (adapted)

Biochemical monitoring for babies on parenteral nutrition should follow the schedule below. N.B. There is insufficient evidence to specify who should be monitored (gestational age, birthweight, steroids, short gut syndrome).

Recommended monitoring for refeeding syndrome

For babies with a birthweight <1,500 g or <10th centile, monitor serum phosphate and calcium on days 3, 5 and 7 and then alternate days until commenced on fortified breastmilk or preterm formula.

Urea

Limiting amino acid intake based on serum urea alone is not warranted. Urea levels up to 14 mmol/L may be considered acceptable in infants on parenteral nutrition provided there are no other parameters to suggest protein intolerance (e.g. hyperammonaemia >122 μmol/L).

Triglycerides

The routine monitoring of plasma triglyceride concentrations is not recommended.

Also linked to Parenteral Nutrition Question 8 “Are there any indications (e.g. high triglycerides, sepsis) to wean, reduce or restrict parenteral lipid administration?” (AA8)

Biochemical monitoring for babies on parenteral nutrition
Investigation Neonatal reference range Before clinical and metabolic stabilisation   Once clinically and metabolically stable    
    Every 1–2 days As required*  Every 1–2 weeks After one month on PN, then monthly As required*
Glucose 2.6–6.5 mmol/L X   X    
Blood gases (capillary) pH 7.35–7.45, PCO2 4.7–6.0 kPa, HCO2 22–26 mmol/L
 X   X    
Sodium 135–145 mmol/L X   X    
Potassium 3.5–6.0 mmol/L X   X    
Chloride 90–114 mmol/L X       X
Calcium Total 2.0–2.7 mmol/L, Ionised 1.1–1.3 mmol/L
 X     X  
Phosphorus 1.4–2.5 mmol/L (see footnote for frequency)  X     X  
Magnesium 0.65–1.0 mmol/L   X     X
Zinc 9–17 μmol/L   X     X
Total protein 45–75 g/L
   X     X
Albumin 25–40 g/L   X     X
Blood urea 1.4–5.0 mmol/L   X     X
Creatinine 20–70 µmol/L    X     X
Triglycerides <3 mmol/L    X     X
Bilirubin (conjugated) <17 µmol/L   X   X  
AST <100 U/L   X   X  
ALT <45 U/L   X   X  
GGT <200 U/L   X   X  
ALP 100–500 U/L (up to 1000 U/L in growth phase)   X   X  
PTH 1.6–6.9 pmol/L   X   X  
Vitamin A  0.7–1.5 µmol/L (200-430 µg/L)   X   X  
Vitamin B12 170–800 pmol/L   X   X  
Vitamin D  >50 nmol/L   X   X  
Vitamin E

11–46 µmol/L Starship
5 – 50 μmol/L Waikato
23-70 μmol/L Christchurch
   X   X  
INR  Lab-dependent norm   X   X  
Trace elements: Se, Zn, Cu
 Lab-dependent norms         X 
C-reactive protein    0–5 mg/L   X     X
Iron  10-31 μmol/L
   X     X
Ferritin 25–200 µg/L   X     X
Urine electrolytes   Urinary Na >30 mmol/L adequate for growth         X

AST aspartate aminotransferase, ALT alanine aminotransferase, GGT gamma-glutamyl transferase, ALP alkaline phosphatase, INR International normalised ratio (an elevated INR may indicate vitamin K deficiency), PTH parathyroid hormone, PN parental nutrition
*no routine monitoring is recommended. Individualised monitoring may be needed based on the clinical situation.
Neonatal reference ranges are used by NZ laboratories

Subgroup considerations

Extremely preterm or metabolically unstable infants require more intensive and frequent testing; stable infants may require reduced frequency.

Implementation considerations

Protocols should specify monitoring intervals and available tests. Regional centres may need referral pathways or courier services for specialist assays.

Monitoring and evaluation

Audit testing compliance, turnaround time, complication rates and frequency of critical abnormal results to guide practice improvement.

Research priorities

  • Define optimal monitoring frequency; validate predictive biochemical markers of nutrient adequacy and toxicity; evaluate less invasive testing strategies.

Question 53. Recommendations for biochemical monitoring of enteral nutritional adequacy for vitamin D, zinc, full blood count, ferritin, sodium, potassium, phosphate, blood glucose, blood urea nitrogen, prealbumin and albumin, conjugated bilirubin, bone mineral status (alkaline phosphatase, calcium, phosphate, vitamin D, parathyroid hormone). Who should be monitored and when (gestational age, birthweight, steroids, short gut syndrome)?

Recommendation (adapted)

Biochemical monitoring of enteral nutrition:

  • Zinc: Consider measuring serum zinc in infants with faltering growth and low serum alkaline phosphatase, especially if they have excessive gastrointestinal fluid losses.
  • Urea: Plasma urea concentration can be used to indicate whether standard breastmilk fortification is sufficient to support appropriate growth. More protein may be needed if serum urea is <2.0 mmol/L
  • Bone mineral status: Phosphorus, calcium, ALP and parathyroid hormone status should be monitored regularly
  • Vitamin D: Serum Vitamin D (25-hydroxyvitamin D) should be measured at one month of age in infants born before 32 weeks’ gestation or birthweight <1500 g. If low, adjust dose and monitor every 10 – 14 days until well into the reference range.
  • Urinary sodium: Consider measuring urinary sodium in infants with faltering growth and normal serum sodium.

[Conditional recommendation] 

Subgroup considerations

Extremely preterm or severely unwell infants may require case specific changes to the testing they receive, such as reduced frequency of testing.

Implementation considerations

Protocols should define recommended monitoring intervals and the available investigations, with established referral or courier pathways to ensure regional access to specialised assays.

Monitoring and evaluation

Review compliance with testing protocols, turnaround times, complication rates, and the incidence of critical abnormal results to support quality improvement initiatives.

Research priorities

  • Establish evidence-based monitoring frequency, identify and validate biochemical markers of nutrient sufficiency and toxicity, and explore less invasive testing methodologies.

Question 54. Does access to a specialist neonatal dietitian vs. no access improve preterm infant outcomes?

Recommendation

Neonatal dietitians who meet the Australasian Neonatal Dietitians Network (ANDiN) Neonatal Dietitian Skill Requirements for the level of neonatal care should be embedded within the multidisciplinary neonatal care team.

[Conditional recommendation]

Justification

Despite the very low certainty of evidence from non-randomised implementation studies, access to a specialist neonatal dietitian is associated with improved growth outcomes and more consistent nutrition practice. Justification is based on common sense around knowledge of the often-complex nutritional needs of preterm infants. Access to a neonatal dietitian is likely to improve equity as expert dietetic input is more likely to lead to a consistent approach for all infants around the country. International guidelines recommend the inclusion of dietitians in neonatal teams, reinforcing this as best practice.

Subgroup considerations

While standardisation of neonatal nutrition care is a clear goal, neonatal dietitians have a critical role of in individualising care, where dietitian-led clinical judgement overrides standard protocols particularly for:

  • Fortification strategies
  • Micronutrient supplementation
  • Faltering growth
  • Complex or high-risk infants
  • Consideration of social factors and whānau preferences

Access to a neonatal dietitian is particularly important for units serving large populations of Māori, Pacific and under-resourced communities, who may otherwise receive inconsistent nutrition support.

Implementation considerations

Use British Dietetic Association (BDA)/British Association of Perinatal Medicine (BAPM)/ Australasian Neonatal Dietitians Network (ANDiN) staffing guidelines to inform workforce planning (e.g. 0.1 FTE per Level 3 cot). Recommended neonatal dietetic staffing levels can be calculated using ANDiN-endorsed BDA recommendations. Support smaller units with remote/telehealth access to neonatal dietitians. Prioritise investment in neonatal nutrition roles in under-resourced hospitals that have neonatal intensive care units. Incorporate dietitians into nutrition policy development, growth monitoring, research
and education.

Monitoring and evaluation

Audit the availability of dietetic services across neonatal units by cot level and region.

Research priorities

  • Evaluate long-term outcomes (neurodevelopment, rehospitalisation, growth) associated with access to neonatal dietitians.
  • Conduct cost-effectiveness analyses of neonatal dietitian-led models of care. Investigate parent and whānau experiences of dietitian involvement in neonatal feeding journeys.

Related links