Parenteral nutrition-associated cholestasis (PNAC) is one of the most common complications resulting from administration of parenteral nutrition in neonates. Excess intravenous intake of vegetable oil-based lipid emulsions containing phytosterols is felt to be a major contributing factor. To date, no information is available on plasma phytosterols half-lives in very-low-birth-weight (VLBW) preterm infants with PNAC. In a prospective cohort study, plasma phytosterols (campesterol, stigmasterol and sitosterol) of VLBW preterm infants with PNAC will be measured by gas chromatography-mass spectrometry (GC-MS) during PN administration and also after the stop of intravenous lipid infusion. Plasma phytosterols half-lives will be calculated from the monoexponential decay curves. Blood samples will be weekly collected from 1st to 12th week of life during routine metabolic tolerance analysis or gas-analysis in order to avoid burden of additional phlebotomy. Samples will be collected in ethylenediaminetetraacetic acid-tubes and immediately centrifugated. Plasma will be stored in pyrogallol added-tubes at -20°C until analysis. Saponification reaction will be done using 5-alpha-cholestane as internal standard.

Inclusion Criteria:

• 24 weeks < gestational age < 32 weeks;
• 500 g ≤ birth weight < 1250 g;
• parenteral nutrition with vegetable oil-based lipid emulsions from the first hours of life;
• diagnosis of cholestasis during vegetable oil-lipid infusion (plasma conjugated bilirubin value > 1 mg/dl)
• parental consent;

Exclusion Criteria:

• severe malformations;
• inborn errors of metabolism;
• severe congenital sepsis;
• normal liver functions (plasma conjugated bilirubin under 1 mg/dl during vegetable oil-lipid infusion).

Preterm infants (24 < gestational age < 32 weeks; 500 g ≤ birth weight < 1250 g) with parenteral nutrition-associated cholestasis.