Perhaps the differing ABO antibodies that transferred in utero from a pregnant individual with incongruent blood group to the fetus played a less important role in overall newborn immunity than other passively transferred antibodies in the immediate period after birth, as the newborn’s immune system is gradually built over many weeks or months after birth.5,14 Although 42.9% of infections were urinary, no appreciable association was seen with ABO blood group incongruence. This evidence concerns the gene ABO and infection.