What Are Blood Type and Rh Tests?

  • Medical Author:
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Ask the experts

I am going to be trying to get pregnant soon, and my doctor ordered a Blood Type and Rh test; what are these tests?

Doctor's response

Blood type tests categorize your blood according to the major human blood group (ABO) system. A person's ABO type depends upon the presence or absence of two genes — the A and B genes. These genes determine part of the configuration of the red blood cell surface. Possible ABO blood groups include O, A, B, or AB.

The Rh antigen is another compound that may or may not be present on the surface of red blood cells. The Rh test determines whether this configuration is present ("Rh-positive") or absent ("Rh-negative") on an individual's blood cells.

Rh testing is performed because the difference in Rh blood group types between an Rh-negative mother and her Rh-positive baby can lead to hemolytic disease (a severe condition in which there is breakdown of the red blood cells) of the newborn. If an Rh-negative mother carries an Rh-positive fetus, she may develop antibodies against the Rh component of the baby's red blood cells. These antibodies could cause hemolytic disease of an Rh-positive baby in subsequent pregnancies. Prevention of hemolytic disease of the newborn is carried out by giving Rh-negative mothers Rh0 (D) immune globulin (brand name: RhoGAM) after delivery of an Rh-positive baby. This prevents the mother's immune system from reacting to the Rh-positive blood of any subsequent fetus.

Medically reviewed by John A. Daller, MD; American Board of Surgery with subspecialty certification in surgical critical care


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Reviewed on 6/22/2017