In about a third of all ABO incompatible pregnancies maternal IgG anti-A or IgG anti-B antibodies pass through the placenta to the fetal circulation leading to a weakly positive direct Coombs test for the neonate's blood. However, ABO HDN is generally mild and short-lived and only occasionally severe because: * IgG anti-A (or IgG anti-B) antibodies that enter the fetal circulation from the mother find A (or B) antigens on many different fetal cell types, leaving fewer antibodies available for binding onto fetal red blood cells. * Fetal RBC surface A and B antigens are not fully developed during gestation and so there are a smaller number of antigenic sites on fetal RBCs.
Hemolytic disease of the newborn 
Neonatal meningitis
Neonatal hepatitis
Michelin tire baby syndrome
Neonatal diabetes
Shaken baby syndrome
Twin-to-twin transfusion syndrome
Neonatal toxic shock-like exanthematous disease