This Is What You Need to Know About Rh Factor

This Is What You Need to Know About Rh Factor

According to the International Society of Blood Transfusion, there are over 33 known blood group systems. Blood groups are determined by the type of molecules and antigens present on the surface of red blood cells. The commonest blood group system is known as the ABO and it involves blood groups like A, B, O, and AB.

The rhesus blood group system is the second commonest and it is usually used along with the ABO in classifying blood groups. Simply put, you are Rhesus factor positive if you have the Rhesus factor in your blood and vice versa. So if your blood group is A+ for example, it means you have the A-antigen as well as the Rh factor antigen.

What is Rh Factor?

Rh factor is the short way of saying Rhesus factor. The name ‘rhesus’ factor can be traced to the use of red blood cells extracted from the blood of rhesus monkeys for obtaining the first blood serum. It is a type of protein found on the external surface of your red blood cells which you inherited from either of your parents.

You are Rh-positive if you have the protein, or Rh-negative if you do not have the protein. About 80-85% of people are said to be Rh-positive.

Why You Should Know Your Rh-Factor

Whether you are positive or negative, you have nothing to worry about as this does not affect your overall health in any way. You should only be concerned about it if you are going to have a blood transfusion or if you are pregnant.

This is because incompatibility can cause blood transfusion reactions and even pregnancy complications if you are Rh-negative and your baby is Rh-positive. In such a condition, you and your baby will require special care during and – to some extent even ­– after pregnancy.

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What is Rh Factor Incompatibility?

If your unborn baby is Rh-positive and you are Rh-negative, you are at risk of Rh incompatibility. This only happens when the father is Rh-positive. During this pregnancy, antibodies are formed by your immune system against the Rh antigens of your baby. Antibodies are like soldiers that help to fight off enemies (antigens) that come into the body. Your baby is considered a foreign object, so once there is a mixing of blood from you two, your body will start to produce antibodies that will later destroy the red blood cells of your baby. This process is known as Rh Sensitization.

Rh sensitization usually does not affect your first pregnancy, because the mixing of your blood and that of your baby is likely not to occur until during childbirth. So, the problem begins with your second pregnancy. This can lead to the death of the baby while still in the womb, or the baby will be born with anaemia, jaundice as well as other problems.

This mixing of blood can also occur during a miscarriage, ectopic pregnancy, bleeding during pregnancy, injury to the abdomen, or even tests that require fluids to be withdrawn from your body during pregnancy. For instance:

  1. Amniocentesis: A test in which amniotic fluid – a sample of fluid that naturally surrounds and protects your baby while in the uterus is obtained to check for possible infections and other abnormalities
  2. Chorionic Villus Sampling: This involves the removal of a small part of the placenta for testing
  3. Cordocentesis: This involves taking a sample of your baby’s blood from its umbilical cord

How to Know Your Rh Factor

To know your Rh factor, all you need to do is a simple blood test with no special preparations required. This test is relatively cheap too. A healthcare professional will collect a small amount of blood from a vein in your hand or arm.

When you are pregnant, your blood group will be tested at the booking visit (first antenatal visit); if you are rhesus negative, your doctor might request a test known as antibody screen. This is aimed at determining whether your blood contains Rh antibodies.

Remember the blood soldiers I told you about earlier? If the test comes back positive, it means you are at risk for Rh incompatibility, but there is no need for you to worry.

What to Do If You Are at Risk of Rh Incompatibility

Now that healthcare professionals have confirmed that you have Rh antibodies that could destroy the red blood cells of your unborn baby and put them at risk, here is what can be done to keep your baby safe:

The doctors will keep a close watch on your baby’s health throughout pregnancy; some will need a blood transfusion immediately after birth because their red blood cells have been destroyed by the antibodies formed by your body; some will need the blood transfusion even before birth, while some will not require any transfusion at all.

If you are Rh-negative but no Rh antibodies were found in your blood, you will receive an injection known as RhoGAM. This injection will prevent the formation of those antibodies. It is usually given in the 28th week of pregnancy or within three days of possible exposure to Rh-positive blood from the baby as may occur from miscarriage, amniocentesis, chorionic villus sampling, trauma, etc. as mentioned earlier.

RhoGAM injection can also be given to Rh-negative people who have been transfused with Rh-positive blood to prevent blood transfusion complications that may occur. In addition, there is now a new method of testing your unborn baby’s Rhesus factor, so with this, you might not even need to be given the injection after all. 


Now that you know this, I hope you and other women will always go early for antenatal care so that issues like rhesus incompatibility can be detected on time and managed appropriately. Also, to the unmarried ones out there, once you have found the man/woman of your dreams, rhesus factor difference is not enough a reason to stop you from tying the knot.

Do you have any questions or contributions to make? Please do not hesitate to let us know in the comment section.