Rh/ABO

Hemolytic Disease of the Newborn

• Aka erythroblastosis fetalis

• From ABO or Rh incompatibility

ABO incompatibility affects first pregnancy

• Mother has anti-A or anti-B IgG (can cross placenta)antibodies

  • Less severe: IgM antibodies (that don't cross placenta) and later development of antigen on fetal RBC

• ↑ risk if mom has O blood

• SSX of neonatal hemolysis

  • Hepatosplenomegaly, jaundice

Rhesus (Rh) incompatibility

• Rh negative mom develops IgG AB from exposure to Rh antigen on Rh positive fetus

• Second pregnancy ➔ hydrops fetalis/fetal hemolysis

  • Neonatal jaundice ➔ ↑ unconjugated bilirubin ➔ kernicterus (encephalopathy)

• Rh typing

  • Rh-negative mothers need screening for anti-D antibodies at initial visit

    • If unsensitized (no anti-D antibodies): Repeat antibody screening at 28wks AND delivery

    • If sensitized (anti-D antibodies >1:8): Amniocentesis/imaging for hemolysis

    • Rosette test confirms if there was fetomaternal hemorrhage

• Anti-D immunoglobulin (RhoGAM)

  • 300µg (1500 IU) IV or IM for every 30mL of fetal blood volume

  • Antibody-mediated immunosuppression for unsensitized, Rh negative mothers

    • RhoGAM doesn't help if mom already developed antibodies

    • Administer at 28wks AND 72hrs after birth of Rh positive baby

  • Also given to Rh negative women s/p ectopic, miscarriage, bleeding in pregnancy, termination, amniocentesis, chorionic villus sampling