Aims To monitor the development of the fecal microbiota of infants during the first year of life, and to investigate the effect of the mode of delivery to the development of gut microbiota.Methods The study included 21 full-term infants, six of the infants were born vaginally and 15 by caesarean section (CS).No infants were treated with antibiotics or probiotics during the period.All of the infants were mixed fed until the introduction of complementary food.