Serum total cholesterol, HDL-cholesterol and VLDL-LDL-cholesterol were determined in 53 newborn infants with gestational ages of 28-42 weeks. In pre-term infants (gestational age less than 37 weeks) the total cholesterol concentration in cord blood was higher than in term infants. Mean values were 2.4 and 1.7 mmol/l, respectively. The HDL-cholesterol/VLDL-LDL-cholesterol ratio was 1.8 in pre-term and term infants. In 11 pre-term and 17 term infants a second determination was made 3-4 days after birth. Total cholesterol had increased more in term than in pre-term infants and the difference found at birth and already levelled out. Mean value was 3.0 mmol/l in pre-term and term infants. The HDL-cholesterol/VLDL-LDL-cholesterol ratio had changed to 0.6 in pre-term and term infants. Six-pre-term infants who received intravenous fluids only were also studied. Their values did not differ from those in pre-term infants fed orally. Free and esterified cholesterol were determined in 26 infants of varying gestational ages. About one-third of the total cholesterol was in the free form in pre-term and term infants at birth and during the first days of life.

Sixteen healthy term infants were followed from birth to the age of 3-6 months. Total cholesterol, VLDL-LDL-cholesterol and HDL-cholesterol were determined in cord serum, in serum obtained 3-10 days after birth (mean age 4.6 days) and at the age of 3-6 months (mean 4.1 months). Mean total cholesterol increased by 1.5 mmol/l during the first 3-10 days and by an additional 1.1 mmol/l during the following 3-6 months. Mean VLDL-LdL-cholesterol increased by 1.0 mmol/l and 0.9 mmol/l, respectively, and mean HDL-cholesterol by 0.4 mmol/l and 0.3 mmol/l, respectively, during the same periods. The HDL-cholesterol: VLDL-LDL-cholesterol ratio thus fell from 1.5 at birth to 0.8 at the age of 3-10 days and to 0.6 at 3-6 months. In eight breast-fed infants, the mean total cholesterol level increased by 2.9 mmol/l from birth to the age of 3-6 months. This increase was significantly higher than the increase found in eight infants who received a cow's milk formula--i.e. 2.3 mmol/l. Free and esterified cholesterol were determined in 10 infants. Free cholesterol accounted for about one-third of the total cholesterol from birth to the age of 3-6 months.

Plasma branched-chain amino acids and urinary C-peptide-creatinine excretion was determined at 3, 4 1/2 and 6 months of age in a group of 50 infants who were either breast-fed or artificially fed and selected at random. The average concentrations of valine in plasma and C-peptide in urine as well as the ratio between C-peptide and creatinine in urine were 2-3 times higher (p less than 0.01) in artificially fed as compared to breast-fed infants at all the ages studied. Plasma valine values correlated significantly with the urinary C-peptide/creatinine ratio (r = 0.76, p less than 0.01), which suggests that the enhanced insulin response induced by the artificial formula is related to its protein content.