Parenteral nutrition associated liver disease (PNALD) in preterm neonates is characterized by early occurrence of intrahepatic cholestasis (parenteral nutrition associated cholestasis (PNAC).

Extreme low birth weight infants (ELBW, birth weight < 1000 g) are at increased risk for development of PNAC.

Important factors implicated in the aetiology of PNAC are high caloric parenteral nutrition using amino acids or dextrose, but also intravenous lipids and infections in particular necrotizing enterocolitis (NEC).

Due to a change of paradigm a more aggressive nutrition with early use of parenteral amino acids/lipids and early fortification of mothers milk or alternatively high caloric preterm formula is warranted. Accordingly - in line with the existing expert opinion and evidence - the feeding policy at the neonatal care units of our hospital was adapted.

Evidence exists that PNAC might be caused by the use of high concentrations of amino acids and lipids in parenteral nutrition. Furthermore NEC is associated with high osmotic feeds. Therefore the incidence of PNAC might be increased directly and indirectly after introducing the new feeding policy.

The investigators therefore aim at retrospectively investigating the incidence of PNAC before and after introduction of a feeding policy of "aggressive nutrition" for ELBW infants.

Inclusion Criteria:

• ELBW infants below 1000 Gram birth weight
• Born in house between January 2005 - December 2006 ("before") and July 2007- June 2009 ("after")

Exclusion Criteria:

• signs of cholestasis at birth
• Death or transfer before 28 Days of life
• Diseases associated with Cholestasis

Preterm Infants below 1000 Gram birth weight