Association of Poor Postnatal Growth with Neurodevelopmental Impairment in Infancy and Childhood: Comparing the Fetus and the Healthy Preterm Infant References

Objectives To compare the classification of preterm postnatal poor growth using healthy preterm vs fetal growth references and to examine associations with neurodevelopmental impairment in infancy and childhood. Study design We included 613 infants born at <33 weeks of gestation. Using the INTERGROWTH-21st (healthy-preterm growth) reference and the Fenton and Olsen (fetal growth) references, we classified poor growth as a decline in z-score from birth to term-equivalent >0.8 SD (weight), >1 SD (head), and >2 SD (length). We used generalized estimating equations to estimate aOR for neurodevelopmental impairment at 18 months and 7 years of corrected age, comparing infants with and without poor growth by each reference, accounting for multiple births and covariates. Results The prevalence of poor growth was higher with INTERGROWTH-21st than with fetal references for all measurements. Agreement was higher between the Fenton and Olsen (fetal) growth references (0.72-0.81) than between INTERGROWTH-21st and fetal references (0.41-0.59). Poor growth by fetal references (but not by INTERGROWTH-21st) was associated with low neurodevelopmental scores in infancy and childhood. Poor weight gain using the Fenton reference was associated with 18-month Mental Developmental Index <85 (aOR 1.6, 95HCl: 1.1, 2.4) whereas poor weight gain by the INTERGROWTH-21st reference was not (aOR 1.0, 95HCl: 0.6, 1.7). Poor linear growth by the Olsen reference, but not INTERGROWTH-21 st , was associated with 7-year verbal intelligence quotient <70 (aOR 3.5, 95HCl: 1.1, 12.7). Conclusions Poor neonatal growth categorized using fetal references showed stronger associations with long term neurodevelopment than poor growth categorized using the INTERGROWTH-21st standards.