The bifidobacteria, including B. infantis, B. bifidum and B. breve, should represent the largest population of beneficial bacteria in babies, whose immune defences are not yet fully working. Babies pick up these friendly bacteria from their mothers during their passage through a clean and healthy birth canal. Studies show that B. infantis was found in approximately 60% of full-term newborns who were born vaginally and only 9% of babies born by caesarean section. Formula fed babies also have significant differences from breastfed babies in the composition of their gut microflora because the heat used to pasteurize formula kills all bacteria. The specific strains used in Infant's Blend have been specially chosen for their value to infant health and have been formulated to the viable count appropriate for infants.