Postnatal Growth of Preterm Infants 24 to 26 Weeks of Gestation and Cognitive Outcomes at 2 Years of Age

BACKGROUND: Weight z scores at 36 weeks of postmenstrual age (PMA) define postnatal growth failure (PGF) and malnutrition. This study aimed to determine weight z scores at 36 weeks PMA that are associated with adverse cognitive outcomes at 2 years of age. METHODS: In this retrospective cohort study, 350 infants 24 to 26 weeks of gestation born between 2006 and 2014 and followed at 2 years were included. Weight z scores at birth and at 36 weeks PMA were calculated using the INTERGROWTH-21st growth curves. The primary outcome was cognitive delay at 2 years of age (Bayley-III cognitive score < 85). RESULTS: Neither the traditional definition of PGF (z score below −1.3) nor the recently proposed definition of malnutrition (z score decline of 1.2 or greater) was associated with cognitive delay. Both a weight z score below −1.0 at 36 weeks PMA (RR: 1.65; 95% CI: 1.10 - 2.49; p <0.05) and a decline below −1.0 in weight z score from birth to 36 weeks PMA (RR: 1.40; 95% CI: 1.00 – 1.94; p <0.05) were associated with a higher risk of cognitive delay. CONCLUSION: With optimal cutoffs, INTERGROWTH-21st weight z scores can predict the risk of cognitive delay.