At birth, infants can be classified either by gestational age (GA) or by weight. Neonates born < 37 weeks are classified as preterm, < 28 weeks as very preterm and < 26 weeks as extremely preterm infants. Prematurely born infants can also be classified by birth weight as follows (1): - Low birth weight (LBW) < 2500 g - Very low birth weight (VLBW) < 1500 g - Extremely low birth weight (ELBW) < 1000 g However, both classifications are used arbitrary in the clinical setting and obviously the infant born very prematurely has most likely a birth weight < 1500 g. Over the past 25 years life support in the neonate born prematurely has improved tremendously and has created major advantages in medical treatment possibilities and survival. Nowadays it is generally accepted to treat the very preterm infant and even the extremely preterm infant since survival rates for these infants are still increasing.

The studies as presented in this thesis were financially supported by the Sophia Foundation for Scientific Research (grant 417) and Numico Research BV, Wageningen.
J.B. van Goudoever (Hans)
Erasmus University Rotterdam
Erasmus MC: University Medical Center Rotterdam