In this project we will examine the associations of fetal and infant growth with behavior and cognitive outcomes in children between 4 and 15 years old. Specifically, we will evaluate the effect of birth weight, gestational age at birth, gestational age adjusted birth weight and internalizing and externalizing problems, attention-deficit hyperactivity disorder symptoms, autism spectrum disorder traits and non-verbal IQ. Furthermore, we will examine the associations of growth patterns between birth weight and infancy body mass index and the same behavior and cognitive outcomes. For this study, we will use harmonized data from birth cohort studies across Europe and analyze this data combined.