In ABO<unk> (also known as ABO HDN) maternal IgG antibodies with specificity for the ABO blood group  system pass through the placenta to the fetal circulation where they can cause hemolysis of fetal red blood cells which can lead to fetal anemia and HDN. In contrast to Rh disease, about half of the cases of ABO HDN occur in a firstborn baby and ABO HDN does not become more severe after further pregnancies.
The ABO blood group system is the best known surface antigen system, expressed on a wide variety of human cells. For Caucasian populations about one fifth of all pregnancies have ABO incompatibility between the fetus and the mother, but only a tiny minority develop symptomatic ABO HDN. The latter only occurs in mothers of blood group O because they can produce enough IgG antibodies to cause hemolysis.
Hemolytic disease of the newborn 
Haemorrhagic disease of the newborn
Neonatal malaria
Neonatal polycythemia
Shaken baby syndrome
Twin-to-twin transfusion syndrome
Neonatal tetanus
Neonatal jaundice