Impact of Neonatal Growth on IQ and Behavior at Early School Age

Abstract

WHAT'S KNOWN ON THIS SUBJECT: Feeding difficulties often emerge during the neonatal period and affect neonatal growth. Growth throughout the first years of life is associated with children' s IQ scores and risk of behavioral problems.WHAT THIS STUDY ADDS: Among infants born full term ($37 weeks' gestation) with birth weight $2500 g, gain in weight and head circumference during the neonatal period is associated with higher IQ, but not with behavior at 6.5 years of age. abstract OBJECTIVES: The objective was to examine associations of neonatal weight gain (NWG) and head circumference gain (HCG) with IQ scores and behavior at early school age. METHODS:We used data from the Promotion of Breastfeeding Intervention Trial, involving Belarusian infants born full term and weighing $2500 g. NWG and HCG were measured as the percentage gain in weight and head circumference over the first 4 weeks relative to birth size. IQ and behavior were measured at 6.5 years of age by using the Wechsler Abbreviated Scales of Intelligence and the Strengths and Difficulties Questionnaire (SDQ), respectively, with SDQ collected from parents and teachers. The associations between the exposures (NWG, HCG) and children' s IQ and SDQ were examined by using mixed models to account for clustering of measurements, and adjustment for potentially confounding perinatal and socioeconomic factors. RESULTS:Mean NWG was 26% (SD 10%) of birth weight. In fully adjusted models, infants in the highest versus lowest quartile of NWG had 1.5-point (95% confidence interval [CI] 0.8 to 2.2) higher IQ scores (n = 13 840). A weak negative (protective) association between NWG and SDQ total difficulties scores was observed for the teacher-reported (b = 20.39, 95% CI 20.71 to 20.08, n = 12 016), but not the parentreported (b = 20.12, 95% CI 20.39 to 0.15, n = 13 815), SDQ. Similar associations were observed with HCG and IQ and behavior. Dr Smithers conceptualized the study and the analysis plan, contributed to the interpretation, and wrote the first draft of the manuscript; Drs Lynch and Yang conceptualized the study and the analysis plan, contributed to the interpretation, and reviewed and revised the manuscript; Mr Dahhou carried out the analysis, and reviewed and revised the manuscript; Dr Kramer designed and supervised the collection of data for the Promotion of Breastfeeding Intervention Trial, conceptualized the current study and the analysis plan, contributed to the interpretation, and reviewed and revised the manuscript; and all authors approved the final manuscript as submitted. CONCLUSIONS:This trial has been registered with the ISRCTN Register