Mutlu M, Irmak E, Aslan Y, Kader Ş. Effects of Lactobacillus rhamnosus GG as a probiotic on neonatal hyperbilirubinemia. Turk J Pediatr 2018; 60: 482-487. Undeveloped intestinal microflora and increased enterohepatic circulation of the newborn contribute to increase of plasma bilirubin level in the first days of life. This study was undertaken to determine the role of probiotic support started immediately after birth on neonatal hyperbilirubinemia in babies born by normal spontaneous vaginal delivery and breastfed only. A total of 150 healthy term newborns were included in the study and allocated in the study and control groups. Immediately after birth, newborns in the study group received probiotic in liquid drop form (Maflor® drops containing Lactobacillus Rhamnosus GG 109 colony forming units, Mamsel Ilac, Turkey), at a dose of 5 drops a day, orally for 10 days. Newborns in the control group received 5 drops of saline solution per day orally, instead. Serum bilirubin levels (cord, 3rd, 5th and 10th days of life) and defecation frequency were recorded. Mean total bilirubin levels on the 3rd, 5th and 10th days were significantly lower and mean defecation frequency was significantly higher in the probiotic group compared to the controls (p < 0.05 for each). Negative correlations were determined between defecation frequency and the 3rd, 5th and 10th day-total bilirubin levels (r=-0.804, p < 0.001; r=-0.818, p < 0.001; r=-0.648, p < 0.001, respectively). Probiotic (Lactobacillus rhamnosus GG) support initiated immediately after birth has a positive effect on bilirubin metabolism and may reduce the risk of hyperbilirubinemia.