Administration of probiotics from the prenatal period through to the first months of life may lead to reduced incidence of eczema5,6 and may also influence the development of infants' Bifidobacterium microbiota.7 Here, we demonstrate that short-term administration of a probiotic strain Lactobacillus rhamnosus GG (LGG) to mothers during late pregnancy can influence intestinal colonization by particular Bifidobacterium species in infants, but does not lead to infant colonization with the administered probiotic. Infants with allergy in Western societies are reported to be less frequently colonized with infant-type Bifidobacterium species such as the B longum group (consisting of B longum biotype infantis, B longum biotype longum, and B bifidum) and B breve, and more frequently colonized by B adolescentis and other species typical of the adult intestinal microbiota than infants without allergy.1,9 Here, we demonstrate that at 90 days of age, infants whose mothers received LGG during late pregnancy were more often colonized with species belonging to the B longum group, the most abundant group of Bifidobacterium microbiota of healthy infant intestine and human breast milk, than infants whose mothers received placebo.\n ...mode of delivery  Placebo, mother not colonized Placebo, mother colonized Probiotic, mother not colonized Probiotic, mother colonized Total LGG present at any time point, n (column %)      No 17 (89) 1 (50) 5 (83) 11 (61) 34 (76) Yes 2 (11) 1 (50) 1 (17) 7 (39) 11 (24) Total 19 (100) 2 (100) 6 (100) 18 (100) 45 (100) B longum present in infant on day 90, n (column %)      No 13 (43) 2 (50) 3 (30) 4 (17) 22 (33) Yes 17 (57) 2 (50) 7 (70) 19 (83) 45 (67) Total 30 (100) 4 (100) 10 (100) 23 (100) 67 (100) B breve present in infant on day 90, n (column %)      No 21 (70) 3 (75) 5 (50) 11 (48) 40 (60) Yes 9 (30) 1 (25) 5 (50) 12 (52) 27 (40) Total 30 (100) 4 (100) 10 (100) 23 (100) 67 (100) B adolescentis present in infant on day 90, n (column %)      No 20 (67) 2 (50) 8 (80) 17 (74) 47 (70) Yes 10 (33) 2 (50) 2 (20) 6 (26) 20 (30) Total 30 (100) 4 (100) 10 (100) 23 (100) 67 (100) B catenulatum present in infant on day 90, n (column %)      No 25 (83) 3 (75) 10 (100) 19 (83) 57 (85) Yes 5 (17) 1 (25) 0 (0) 4 (17) 10 (15) Total 30 (100) 4 (100) 10 (100) 23 (100) 67 (100) low * Colonization of infants with LGG by randomization group and mode of delivery Colonization of infants with Bifidobacterium species by randomization group and mode of delivery Colonization by randomization group and maternal colonization with LGG at delivery  Placebo (n = 31) Probiotic (n = 33) Total (n = 64) Maternal B adolescentis, n frequency (%)    No 16 (52) 21 (64) 37 (58) Yes 15 (48) 12 (36) 27 (42) Maternal B angulatum, n frequency (%)    No 21 (68) 26 (79) 47 (73) Yes 10 (32) 7 (21) 17 (27) Maternal B breve, n frequency (%)    No 28 (90) 30 (91) 58 (91) Yes 3 (10) 3 (9) 6 (9) Maternal B catenulatum, n frequency (%)    No 12 (39) 13 (39) 25 (39) Yes 19 (61) 20 (61) 39 (61) Maternal B lactis, n frequency (%)    No 30 (97) 31 (94) 61 (95) Yes 1 (3) 2 (6) 3 (5) Maternal B longum, n frequency (%)    No 9 (29) 7 (21) 16 (25) Yes 22 (71) 26 (79) 48 (75) low * Colonization of infants with LGG by randomization group and mode of delivery Colonization of infants with Bifidobacterium species by randomization group and mode of delivery Colonization by randomization group and maternal colonization with LGG at delivery Maternal Bifidobacterium colonization at birth by randomization group