Postnatal growth and neurodevelopment at 2 years' corrected age in extremely low birthweight infants.

Background: Faltering postnatal growth in preterm babies is associated with adverse neurodevelopment. However, which growth reference is most helpful for predicting neurodevelopment is unknown. We examined associations between faltering growth and developmental delay in extremely low birthweight (ELBW) infants.

Methods: We categorized faltering growth (z-score decrease ≥0.8 for weight/length, >1 for head circumference) between birth, 4 weeks, 36 weeks' postmenstrual age and 2 years' corrected age using fetal (Fenton, UK-WHO and Olsen) and healthy preterm (INTERGROWTH-21st) references. Associations between faltering growth and developmental delay were examined using binary logistic regression and area under the receiver operating curve (AUC).

Results: In 327 infants, Olsen charts identified the highest prevalence of faltering growth (weight 37%, length 63%, head 45%). Agreement in classification was higher amongst fetal references (kappa coefficient, ĸ = 0.46-0.94) than between INTERGROWTH-21st and fetal references (ĸ = 0.10-0.81). Faltering growth in all measures between 4-36 weeks (odds ratio, OR 2.0-4.7) compared with other time intervals (OR 1.7-2.7) were more strongly associated with developmental delay, particularly motor delay (OR 2.0-4.7). All growth references were poorly predictive of developmental delay at 2 years (AUC ≤ 0.62).

Conclusions: Faltering postnatal growth in ELBW infants is associated with, but is poorly predictive of, developmental delay at 2 years.

Impact: In babies born preterm, different growth references result in wide variation in categorization of faltering postnatal growth. Faltering growth in weight, length, and head circumference from 4 weeks to 36 weeks' postmenstrual age are associated with developmental delay at 2 years' corrected age, particularly motor delay. However, postnatal growth is a poor predictor of later developmental delay in extremely low birthweight infants irrespective of the growth reference used.