Lecture Notes on Blood Group Incompatibility and Rh Incompatibility

Overview

• Topic: Comparison between blood group incompatibility and Rh incompatibility in the context of hemolytic disease of the newborn.

Blood Group Incompatibility

• Frequency & Severity:
  • More common but less severe than Rh incompatibility.
• Conditions:
  • Mother: Blood group O.
  • Fetus: Blood group A or B.
• First Pregnancy:
  • Can be affected; no sensitization required.
• Clinical Signs:
  • Hepatosplenomegaly is less common.
  • Unconjugated hyperbilirubinemia is less common.
  • Jaundice is less common.
  • Hemolytic anemia is less common.
  • Kernicterus is less common.
  • Reticulocytosis is less common.
  • Presence of nucleated red blood cells in blood smear is less common.
• Coombs Test:
  • Weakly positive direct Coombs test.
• Note on Prevention:
  • Incompatibility can prevent Rh sensitization by destroying fetal red blood cells with maternal anti-A IgM agglutinins.

Rh Incompatibility

• Frequency & Severity:
  • Less common but more severe than blood group incompatibility.
• Conditions:
  • Mother: Rh-negative.
  • Fetus: Rh-positive.
  • Blood group (A, B, AB, O) does not affect this.
• First Pregnancy:
  • Safe; sensitization required from a previous pregnancy or event.
• Clinical Signs:
  • Hepatosplenomegaly is more common.
  • Unconjugated hyperbilirubinemia is more common.
  • Jaundice is more common.
  • Hemolytic anemia is more severe.
  • Kernicterus is more common.
  • Reticulocytosis is more common.
  • Presence of nucleated red blood cells in blood smear is more common.
• Coombs Test:
  • Both direct and indirect Coombs tests are strongly positive.
• Pathophysiology:
  • Entire red blood cells are phagocytized by macrophages, indicating severe anemia.

Important Notes

• Protection Mechanism:
  • Incompatibility can act as a protective measure against Rh sensitization when incompatible fetal red blood cells are destroyed by maternal antibodies.

Conclusion

• Key Takeaway:
  • Understanding the distinction between blood group incompatibility and Rh incompatibility is crucial in managing and preventing hemolytic disease in newborns.

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