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What is ABO Group and Rhesus (Rh) Factor?

ABO blood group and Rhesus (Rh) factor are the two most important blood classification systems used to determine your blood type. The ABO system categorizes blood into four main types based on the presence or absence of A and B antigens on the surface of red blood cells: Type A (has A antigens), Type B (has B antigens), Type AB (has both A and B antigens), and Type O (has neither A nor B antigens). The Rh factor is determined by the presence or absence of the D antigen on red blood cells. If you have the D antigen, you are Rh positive (Rh+), and if you lack it, you are Rh negative (Rh-). Together, these two systems create eight primary blood types: A+, A-, B+, B-, AB+, AB-, O+, and O-.

Why is ABO Group and Rh Factor important?

Knowing your ABO blood group and Rh factor is critical for safe blood transfusions and organ transplants. Receiving incompatible blood can trigger a severe immune response that destroys red blood cells, leading to potentially life-threatening complications. The Rh factor is particularly important during pregnancy. If an Rh-negative mother carries an Rh-positive baby, her immune system may produce antibodies against the babyโ€™s blood cells, a condition called Rh incompatibility. This can cause hemolytic disease of the newborn in subsequent pregnancies if not properly managed with Rh immunoglobulin (RhoGAM) injections.
Blood type also plays a role in compatibility for organ donation and has been associated with varying susceptibility to certain diseases. For example, research studies have shown correlations between blood type and cardiovascular disease risk, infectious disease susceptibility, and other health conditions.

How can I better understand my ABO Group and Rh Factor?

ABO Blood Groups:

  • Type A: Has A antigens on red blood cells and anti-B antibodies in plasma
  • Type B: Has B antigens on red blood cells and anti-A antibodies in plasma
  • Type AB: Has both A and B antigens on red blood cells and no anti-A or anti-B antibodies (universal plasma donor)
  • Type O: Has no A or B antigens on red blood cells and both anti-A and anti-B antibodies (universal red cell donor)

Rh Factor:

  • Rh positive (Rh+): Has D antigen present on red blood cells (approximately 85% of the population)
  • Rh negative (Rh-): Lacks D antigen on red blood cells (approximately 15% of the population)

Blood Type Distribution (United States):

  • O+ : 37-38%
  • A+ : 34-36%
  • B+ : 8-9%
  • O- : 6-7%
  • A- : 6%
  • AB+ : 3-4%
  • B- : 1-2%
  • AB- : <1%

Your blood type is determined genetically and remains constant throughout your life. Blood typing is performed through laboratory tests that identify the presence or absence of specific antigens and antibodies in your blood sample.

What does my blood type mean for transfusions?

Blood transfusion compatibility depends on matching donor and recipient blood types:
Red Blood Cell Transfusions: You can receive red blood cells from donors whose blood type is compatible with yours. Type O- is the universal red cell donor (can donate to all blood types), while Type AB+ is the universal red cell recipient (can receive from all blood types). Generally, you can receive blood from your own type or from compatible types based on ABO and Rh matching.
Plasma Transfusions: Plasma compatibility works in reverse. Type AB is the universal plasma donor, while Type O is the universal plasma recipient.
Pregnancy Considerations: If you are an Rh-negative woman, your healthcare provider will monitor your pregnancy closely and may administer RhoGAM injections at 28 weeks of pregnancy and after delivery if your baby is Rh-positive to prevent Rh incompatibility issues in future pregnancies.

Where can I learn more?

DISCLAIMER: This information is for educational purposes only and is not a substitute for professional medical advice. Always consult your healthcare provider for interpretation of your blood type results and for personalized health recommendations.