Factors affecting the severity of neonatal jaundice of unknown etiology: the role of enterohepatic circulation.

Jaundice is the most common condition of otherwise healthy, full-term newborns during the first week of life, and Chinese newborns are known to have a higher incidence and severity of neonatal jaundice than Caucasian newborns. This prospective study was designed to examine factors affecting the severity of neonatal jaundice of unknown etiology in the first week of life with special emphasis on the role of enterohepatic circulation. One hundred and thirty-six healthy, full-term newborns were enrolled in this study. Serum bilirubin levels were monitored daily in the morning for the first five days after delivery. Cord blood, postpartal maternal blood, breast milk and infants' stools were analyzed for beta-glucuronidase activity. Infants with serum peak bilirubin level less than or equal to 7 mg/dl had older gestational age, less maximal weight loss and the bilirubin levels peaked at an earlier age than those infants with peak serum bilirubin level more than 7 mg/dl. They also had lower fecal beta-glucuronidase activity in the stool collected at a mean age of 4.5 (+/- 0.6) days. Among the 136 study cases, 92 infants received some maternal breast milk. There was considerable amount of beta-glucuronidase activity in the human breast milk. Yet its presence did not affect the fecal enzyme activity. Mixed breast feeding also did not influence the serum bilirubin level in the first four days of life. However, infants fed dominantly with breast milk had a higher incidence of serum bilirubin level more than 10 mg/dl at five days old than infants fed solely by infant formula.(ABSTRACT TRUNCATED AT 250 WORDS)