Mean ( SD ) total serum bilirubin levels in zinc and placebo groups were 13.9 ( 2.5 ) vs. 13.4 ( 1.9 ) mg/dL ( mean difference 0.566 ; 95 % CI -0.535 , 1.668 , P = 0.038 ) at 48 h , 13.1 ( 2.7 ) vs. 12.8 ( 2.3 ) mg/dL ( mean difference 0.234 ; 95 % CI -1.011 , 1.479 , P = 0.708 ) at 96 h and 8.0 ( 2.0 ) vs. 8.6 ( 1.2 ) mg/dL ( mean difference -0.569 , 95 % CI -1.382 , 0.242 , P = 0.166 ) at 144 h. Although the mean duration of phototherapy in the zinc group was less by 21.3 h ( 95 % CI 11.6 , 30.9 , P = 0.052 ) , the difference was not significant .