How Should We Define Postnatal Growth Restriction in Preterm Infants?

Area of Science:

• Neonatalogy
• Pediatric Neurodevelopment
• Growth Monitoring

Background:

• Postnatal growth restriction is prevalent in preterm infants and may impact neurodevelopment.
• Current definitions of postnatal growth restriction lack biological validation and vary across studies.
• Accurate definition is crucial for understanding its association with neurodevelopmental impairment.

Purpose of the Study:

• To investigate the association between neurodevelopmental outcomes and postnatal growth restriction in preterm infants.
• To compare two different definitions of postnatal growth restriction.
• To identify a more reliable method for defining and assessing growth restriction.

Main Methods:

• 168 preterm infants were assessed at 2 years corrected age using the Bayley Scales of Infant Development-II.
• Postnatal growth restriction was defined in two ways: weight z-score <-1.5 at 36 weeks, or as a continuous variable (fall in weight z-scores from birth to 36 weeks).
• Statistical analysis adjusted for gestational age and small for gestational age at birth.

Main Results:

• A significant weight z-score decline was observed in 98.8% of infants; 44.1% met the <-1.5 threshold at 36 weeks.
• Each 1-point decrease in weight z-score from birth to 36 weeks was linked to a 5.6-point reduction in the Mental Developmental Index.
• A weight z-score <-1.5 at 36 weeks did not show a significant association with poorer mental or psychomotor development.

Conclusions:

• A falling weight z-score from birth to 36 weeks is a more biologically relevant definition of postnatal growth restriction.
• This definition demonstrates predictive value for neurodevelopmental outcomes in preterm infants.
• The findings suggest a revised approach to defining and monitoring growth restriction in this population.