Inclusion Criteria:  Former patient of the Department of Neonatology of the University Hospital Zurich Born between 01.01.2019 and 31.12.2021, i.e. aged 18 to 30 months at the time of the research visit Gestational age below 370/7 weeks Parent consent  Exclusion Criteria:  Genetically defined syndrome (including chromosomal aberration) or inborn error of metabolism adversely influencing life expectancy or neurodevelopment. Major congenital malformations requiring surgical correction or potentially affecting neurodevelopmental outcome. Hypoxic ischemic encephalopathy after perinatal asphyxia defined as grade 2 or 3 according to Sarnat and Sarnat[19]. Neonatal drug withdrawal syndrome or known maternal substance consumption of following illicit drugs during pregnancy: cocaine, heroin, Lysergic acid diethylamide (LSD), 3,4-Methylenedioxymethamphetamine (ecstasy), phencyclidine (PCP), and other amphetamine/methamphetamine. Children of parents who are not speaking German