The purpose of this study is to determine plasma phytosterols half-lives in preterm infants who received intravenous soy oil-based lipid emulsions.

Several studies reported the relationship between plasma phytosterol concentrations and parenteral nutrition-associated cholestasis (PNAC). Information on plasma phytosterols half-lives in very-low-birth-weight (VLBW) preterm infants on lipid parenteral nutrition (PN) are lacking. In a prospective cohort study, plasma phytosterols (campesterol, stigmasterol and sitosterol) of VLBW preterm infants on routine PN will be measured by gas chromatography-mass spectrometry (GC-MS) during PN administration and after only lipid stopping. Plasma phytosterols half-lives will be calculated from the monoexponential decay curves. Blood samples will be weekly collected from 1st to 7th 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 soy oil-based lipid emulsions from the first hours of life;
• parental consent.

Exclusion Criteria:

• length of parenteral nutrition > 24 days;
• severe malformations;
• inborn errors of metabolism;
• severe congenital sepsis;
• liver dysfunctions.

Preterm infants (24 weeks < gestational age < 32 weeks; 500 g ≤ birth weight < 1250 g) who received intravenous soy oil-based lipid emulsions from the first hours of life.