Urinary D-glucaric acid excretion in idiopathic neonatal jaundice

To determine the extent to which immaturity of hepatic microsomal enzyme activity might contribute to physiological jaundice.

Urinary excretion of D-glucaric acid, expressed in mumol glucaric acid/ mmol creatinine, was measured in 122 Chinese full-term healthy newborn babies during the first five days of life. Among the 122 babies, 22 were born by normal spontaneous delivery at the British Military Hospital and 100 were born by caesarean section at the Prince of Wales Hospital.

In all babies the excretion of D-glucaric acid was highest on the first day of life and gradually decreased over the following 5 days. Five babies born by spontaneous delivery and six babies born by caesarean section developed jaundice during the study period. The excretion of D-glucaric acid in the jaundiced babies was significantly higher on the first two days than in the non-jaundiced babies.

D-glucaric acid excretion was increased in jaundiced newborn babies in the first few days of life. This finding does not indicate less liver microsomal enzyme activity in the jaundiced babies compared to those non-jaundiced. On the contrary, it suggests that in idiopathic neonatal jaundice compensatory mechanism might operate from a very early stage to excrete a higher bilirubin load that might be present through haemolysis.