The probiotic tablets and the probiotic oil (at the recommended dose) contain 2x10^8 CFU of Lactobacillus reuteri. Both the placebo tablets and oil are identical in size and composition but without the addition of the probiotic strains. The tablets and oil are packed in identical pots/bottles with color coding. The code will be kept from the investigators until the analysis are finished. Both the tablets and oil are provided by BIOGAIA AB.