An Rh woman refers to a woman who has a certain type of protein on the surface of her red blood cells. This protein is known as the Rh factor or Rh antigen. The Rh factor is inherited from your parents through your genes.
The Rh Blood Group System
There are four main blood group systems – ABO, Rh, Kell and Duffy. The most important of these is the ABO blood group system, but the Rh system is the next most significant.
The Rh system contains over 50 different blood group antigens. The most important of these is the RhD antigen. If your red blood cells have the RhD antigen, you are Rh positive (Rh+). If your red blood cells lack the RhD antigen, you are Rh negative (Rh-).
Being Rh positive or Rh negative refers only to the presence or absence of the RhD antigen. There are many other Rh antigens that can be present or absent. However, only the RhD antigen is commonly tested for.
Rh Positive vs Rh Negative Blood
Most people are Rh positive – around 85% of people. The other 15% of people are Rh negative.
There are no differences between Rh positive and Rh negative blood in terms of quality, makeup or function. The only difference is the presence or absence of the RhD antigen.
Both Rh positive and Rh negative individuals have the same types of red blood cells. The difference lies in proteins found on the surface of these cells – Rh positive red blood cells have the RhD antigen, whereas Rh negative cells do not.
Rh Positive Blood
85% of people are Rh positive. This means their red blood cells have the RhD antigen on them.
Being Rh positive is not considered a condition that requires treatment. Most people are Rh positive and it does not affect their health.
However, it can become an issue during pregnancy if the mother is Rh negative and the fetus is Rh positive (see section below on Rh incompatibility during pregnancy).
Rh Negative Blood
15% of people are Rh negative. This means their red blood cells lack the RhD antigen.
Again, being Rh negative is not considered a disease and does not by itself affect your health. However, it can become an issue during pregnancy.
It also means you should only receive Rh negative blood during a transfusion. Getting Rh positive blood could lead to complications.
Rh Status Inheritance
The Rh antigen is inherited from your biological parents. Your Rh status is determined by the Rh genotypes of your parents.
The Rh gene has two variations – Rh+ and Rh-. Each person inherits one from their mother and one from their father.
If you inherit two Rh+ genes, you will be Rh positive. If you inherit one Rh+ gene and one Rh- gene, you will still be Rh positive (Rh+ is dominant over Rh-). The only way to be Rh negative is to inherit two Rh- genes – one from each parent.
Here is how Rh status is typically inherited:
- If both parents are Rh+: The child will be Rh+
- If one parent is Rh+ and one is Rh-: The child will be Rh+
- If both parents are Rh-: The child will be Rh-
Rh negative status can seem uncommon because both parents need to at least carry the Rh- gene in order to have an Rh negative child. This is why Rh negative individuals make up a relatively small proportion of the population.
Rh Incompatibility During Pregnancy
Rh status becomes important during pregnancy if the mother is Rh negative and the father is Rh positive. This is called Rh incompatibility.
If the fetus inherits Rh+ status from the father, its red blood cells will have the Rh antigen. However, the mother’s immune system will see this Rh antigen as foreign and may produce antibodies against it.
This usually does not cause problems in a first pregnancy. However, during subsequent pregnancies, the Rh antibodies can cross the placenta and attack the fetus’ Rh positive red blood cells. This can lead to hemolytic disease of the newborn.
To prevent this, Rh negative mothers are given a medication called Rh immunoglobulin (RhIg). This prevents the mother’s immune system from making antibodies against the fetus’ blood cells. RhIg has made hemolytic disease of the newborn much less common.
Hemolytic Disease of the Newborn
Hemolytic disease of the newborn (HDN) is a blood disorder that occurs when the Rh positive fetus of an Rh negative mother is attacked by the mother’s Rh antibodies.
The mother’s Rh antibodies were likely produced during a previous Rh incompatible pregnancy. They can cross the placenta and destroy the fetal red blood cells.
This can lead to anemia, jaundice and swelling in the fetus and newborn baby. In severe cases it can cause serious complications such as brain damage.
Preventing HDN
All Rh negative pregnant women should receive Rh immunoglobulin (RhIg) injections during pregnancy to prevent Rh incompatibility issues.
RhIg blocks the mother’s immune system from “seeing” the Rh antigen. This prevents her body from creating antibodies against the fetus’ Rh positive blood.
RhIg injections have made hemolytic disease of the newborn much less common nowadays.
Blood Transfusions and the Rh Factor
The Rh factor must also be considered when giving someone a blood transfusion. People who are Rh negative can only receive Rh negative blood.
Getting Rh incompatible blood can lead to a dangerous transfusion reaction. The Rh antibodies from the donor blood can attack and destroy the recipient’s red blood cells.
Before getting a transfusion, blood banks will test your blood type for both the ABO antigens and the Rh antigen. This ensures the donated blood matches your Rh status.
Testing for the Rh Factor
The common tests used to determine your Rh status include:
- Blood typing – A blood sample is analyzed to detect the presence or absence of Rh antigens.
- Coombs test – Also called an indirect Coombs or antibody test. Checks for antibodies against the Rh antigen.
- Elution test – Separates antibodies from red blood cells to identify the type.
These blood tests can determine if you are Rh positive or Rh negative. They may be ordered as part of routine prenatal care, before surgery or before getting a blood transfusion.
Who Needs to Know Your Rh Status?
It’s important for certain medical professionals to know your Rh status. This includes:
- Your doctor before pregnancy, surgery or transfusion
- Emergency and operating room staff before procedures
- Your OB/GYN – critical during pregnancy
- Medical staff if admitted to hospital
Wearing a medical alert bracelet can inform providers of your Rh negative status when needed.
Advantages of Being Rh Negative
While being Rh negative can cause issues during pregnancy, there are some potential advantages:
- May provide protection against some pathogens like HIV and hepatitis
- Lower risk for some autoimmune conditions
- Improved tolerance of transfusions for conditions like thalassemia
Researchers are still investigating why being Rh negative seems to be linked to these potential benefits.
Key Takeaways
- An Rh woman is one who has Rh negative blood type.
- The Rh blood group refers to the presence or absence of the Rh antigen.
- Most people are Rh positive. Only 15% of people are Rh negative.
- Rh status is inherited from your parents.
- Rh incompatibility between mother and fetus can occur during pregnancy.
- Rh immunoglobulin prevents the mother’s body from attacking an Rh positive fetus.
- Rh negative individuals can only receive Rh negative blood.
- Doctors need to know your Rh status before procedures, pregnancy and transfusions.
Conclusion
Your Rh status refers to whether you are Rh positive or Rh negative. This is determined by the presence or absence of the RhD antigen on your red blood cells.
Being Rh negative is not a disorder, it just means your blood lacks this one specific antigen. However, it can lead to complications during pregnancy if proper precautions are not taken.
Most people are Rh positive, but around 15% of the population is Rh negative. Your Rh status is inherited from your biological parents.
It’s important for your doctor to know your Rh type in case you need a blood transfusion or before undergoing surgery or childbirth. Understanding your Rh status helps prevent potentially dangerous blood reactions.