Birth-weight centile at term and school performance at 12 years of age: linked cohort study

Objective: Birth weight, fetal growth and placental function influence cognitive development. The gradient of these associations is understudied, especially among those with a birth weight considered appropriate-for-gestational age. The aim of this study was to evaluate the associations between birth-weight centile and intellectual development in term/near-term infants across the entire birth-weight spectrum, in order to provide a basis for better understanding of the long-term implications of fetal growth restriction and reduced placental function. Methods: This was a population-based cohort study of 266 440 liveborn singletons from uncomplicated pregnancies, delivered between 36 and 42 weeks of gestation. Perinatal data were obtained from the Dutch Perinatal Registry over the period 2003–2008 and educational data for children aged approximately 12 years were obtained from Statistics Netherlands over the period 2016–2019. Regression analyses were conducted to assess the association of birth-weight centile with school performance. The primary outcomes were mean school performance score, on a scale of 501–550, and proportion of children who reached higher secondary school level. Results: Mean school performance score increased gradually with increasing birth-weight centile, from 533.6 in the 1^st–5^th birth-weight-centile group to 536.8 in the 81^st–85^th birth-weight-centile group. Likewise, the proportion of children at higher secondary school level increased with birth-weight centile, from 43% to 57%. Compared with the 81^st–85^th birth-weight-centile group, mean school performance score and proportion of children at higher secondary school level were significantly lower in all birth-weight-centile groups below the 80^th centile, after adjusting for confounding factors. Conclusions: Birth-weight centile is associated positively with school performance at 12 years of age across the entire birth-weight spectrum, well beyond the conventional and arbitrary cut-offs for suspected fetal growth restriction. This underlines the importance of developing better tools to diagnose fetal growth restriction and reduced placental function, and to identify those at risk for associated short- and long-term consequences.