High direct bilirubin. Between these?

My baby is 45 days old now. His direct bilirubin content at birth was 0.4 mg/dl and total bilirubin content was 11 mg/dl. On 45th day his direct bilirubin content is 1.4 mg /dl and total bilirubin content is 8 mg/dl. He has been given only mother's milk since birth. he is feeding well. His birth weight was 3.9 kg at birth and now he weighs 5.8 kg. The baby is urinating atleast 9 times in 24 hours and he is pooing atleast 4 times in 24 hours. His stool is yellow in colour.My doctor advised to check the liver function of the baby as his direct bilirubin content has been raised. Is it a serious problem?? My baby's left renal pelvis size was 8.1 mm during my 9th month growth scan and so the doctor advised to take abdomen scan for the baby when he is 3 months old. Is there any link between these??