Serum bile acids in newborns: evidence for an hepatic dysfunction in low-birth-weight infants.

The post-prandial pattern of total serum bile acids was studied in 47 newborns: 12 prematures (less than 36 weeks), 17 term low-birth-weight infants (less than the 3rd percentile), 18 term normals. The study was made at the end of the first month. Blood was collected in a peripheral vein using a microcatheter. Samples were taken at fasting time and 30, 60, 120, 180 min after a test meal intake (40 ml/kg of "humanized" milk based formula). Bile acids were assayed using an original enzymatic micromethod which needed only 50 microliter of serum and showed a sensitivity of 0.3 pmol in 200 microliter of reaction medium. The response of serum bile acids after the test meal was very similar in normal term newborns and in adults. Prematures exhibited bile acid levels slightly higher than normals, but this difference was significant only at 0 and 180 min. Low-birth-weight infants showed very high values of serum bile acids at all times during the test, compared to normal and premature infants. Serum levels of total bilirubin and alkaline phosphatase were similar in all 3 groups. These results are not consistent with cholestasis but rather indicate a specific dysfunction in bile acid metabolism in low-birth-weight infants.