Neonatal Cord Blood Screening for HDN

Hemolytic disease of the newborn (HDN) refers to fetal or neonatal alloimmune hemolysis caused by red blood cell antibodies due to incompatible maternal and fetal or neonatal blood types. A French midwife first described the disorder in 1609; however, it was not until the 1950s when the underlying cause was clarified. The pathogenesis of HDN begins with the attack of fetal red blood cells (RBCs) by maternal antibodies due to incompatibility of maternal and fetal blood. Immunologically, antibody secretion initially starts with Immunoglobulin M (IgM), which cannot cross the placental barrier, but is then followed by isotype switching, which produces Immunoglobulin G (IgG) antibodies. IgG antibodies can cross the placental barrier, and they do so during the second and or subsequent pregnancies, attacking the fetal RBCs and causing hemolysis and associated complications such as Hydrops fetalis and jaundice. HDN can occur due to Rh antigens, most commonly the D antigen, and A,B and O RBCs antigens (ABO) antigens. Rh(D)-HDN has decreased since the introduction of antenatal and postpartum Rh immunoglobulin. Therefore, the prevalence of HDN, nowadays, varies according to blood type incompatibility. ABO incompatibility is the most common cause of HDN and Rh (D) antigen is the second most common cause.\[8\] Rh (C, c, E, e) antigen incompatibility occurs occasionally. Several other alloantibodies have also been reported to be associated with hemolytic diseases, including Kidd, Diego, Duffy, Kell and Anti-Mur. Minor blood group incompatibility due to blood groups other than Rh(D), although an uncommon cause of neonatal hyperbilirubinemia, has the potential to cause severe hyperbilirubinemia and its sequelae in infants, if left undiagnosed and untreated. Therefore, identification of at-risk cases will help clinicians to reduce neonatal morbidity and will result in better patient management