The investigators want to investigate whether there are compensatory mechanisms in placentas of premature born infants and whether the maternal thyroid hormone condition is a prediction of the development of THOP in the premature infant. The investigators want to investigate the differences between several groups of preterm infants: 24-28 weeks, 28-32 weeks and 32-36 weeks. The further aim of this study is to investigate the impact of maternal thyroid hormone condition during pregnancy on neurodevelopmental outcome of the neonate.