Moroni quotes an epistle from Mormon which speaks out strongly against infant baptism in the 4th Century A.D (see Moroni 8:4-26). Among other things Mormon says:
And little children need no repentance, neither baptism. . . . And he that saith that little children need baptism denieth the mercies of Christ, and setteth at naught the atonement of him and the power of his redemption. . . . And after rejecting so great a knowledge, my son, they [the Nephites] must perish soon . . . (Moroni 8:11, 20, 29)
Apparently, despite Mormon's preaching, the practice of infant baptism continued until the arrival of the Spaniards. Bernardino de Sahagun described the Aztec baptism of infants. H.H. Bancroft wrote of it as follows:
Then the midwife dipped the child into water and said: "Enter, my son, into the water . . . let it wash thee; let him cleanse thee . . . let him see good to put away from thee all the evil that thou has carried with thee from before the beginning of the world. (Native Races, Vol. 3, p. 370)
[Roy E. Weldon and F. Edward Butterworth, Book of Mormon Claims and Evidences, Vol. 2, p. 94]