SERPINB2 and newborn respiratory distress syndrome: Moreover, Brus et al. [9] reported increased tissue-plasminogen activator (t-PA) levels in preterm infants with RDS in the first 6-12 h after birth, while Yurdakok et al. [55] found normal t-PA levels, but increased plasminogen activator inhibitor (PAI) levels in preterm neonates with RDS in their first 6 h of life.