Participants
syndrome affecting cognitive development, congenital anomalies
The participants were born to Finnish- or Swedish-speaking families in Turku University Hospital, Finland, between 2002 and 2004. The inclusion criteria were birth weight ≤1500 g and gestational age < 37 weeks. From the beginning of 2004, the inclusion criteria were expanded to include all infants born < 32 gestational weeks, despite the birth weight. The exclusion criteria were severe congenital anomalies or a diagnosed syndrome affecting cognitive development. The control group consisted of healthy full term (> 37 weeks) infants born at Turku University Hospital during the same period. Families were informed about the host PIPARI Study protocol in the neonatal intensive care unit (very preterm infants) or at the newborn nursery (full term controls). At the 17-year age-point, all the adolescents born between 2002 and 2004, and their parents were included in this study. The flowchart of the participants is shown in Fig. Flowchart of the study participants