HomeGynaecology CareWhat Is Rh factor? How Is It Important During Pregnancy?

What Is Rh factor? How Is It Important During Pregnancy?

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The Rhesus factor, commonly called the Rh factor, is a type of protein found on blood cells in the body. People are either Rh-positive, showing they have the protein, or Rh-negative, without this protein. It is important to note if the mother is Rh-negative and the child is Rh-positive. 

This article will discuss the Rh factor screening test and its importance during pregnancy.

What is the Rh factor?

As mentioned, Rhesus (Rh) factor is an inherited protein found on the surface of red blood cells. If the blood in an individual’s body has the protein, a person is Rh-positive. A person is Rh-negative if their body lacks the Rh factor.

Rh-positive is the most common blood type. Although an Rh-negative blood type is not an illness and usually does not affect a person’s health, it may affect pregnancy. The pregnancy needs exceptional care if the woman is Rh-negative and the baby is Rh-positive (Rh incompatibility). A baby may inherit the Rh factor from either of the parents.

Doctors recommend a blood type and Rh factor screening test during a woman’s first prenatal visit. It will help identify whether the maternal blood cells carry the Rh factor protein or not.

What is Rh incompatibility?

It is called Rh incompatibility when a woman with Rh-negative is pregnant with a baby having Rh-positive blood. Due to Rh incompatibility, the woman’s immune system reacts and creates Rh antibodies. These antibodies drive an immune system attack against the baby, which the woman’s body identifies as an invader.

When women with RhD negative blood are exposed to RhD positive blood, generally during pregnancy with an RhD positive baby, their body responds to the RhD positive blood by producing antibodies (infection-fighting molecules). These infection-fighting molecules identify and destroy the foreign blood cells.

If sensitisation happens, the next time a woman is exposed to RhD positive blood, her body will immediately produce antibodies. If a woman pregnant with RhD positive baby, the antibodies may cross the placenta, causing rhesus disease in the unborn infant. The antibodies can continue attacking the baby’s red blood cells for a few months after birth.

What complications are associated with Rh incompatibility?

Rh incompatibility does not cause an effect in a pregnant woman. But babies may develop hemolytic anaemia – in which a baby’s red blood cells break down quicker than the doctor can replace the red blood cells.

The effects of this hemolytic anemia can range from mild to severe. These effects may include complications such as jaundice, liver failure, and heart failure. Doctors need to treat this condition quickly, depending on its severity.

  • For mild cases, there may be no necessary treatment.
  • In severe cases, the doctors may recommend that the baby receive a blood transfusion through the umbilical cord ensuring quick replacement of the baby’s red blood cells.
  • The doctors treat babies who have jaundice or show signs of an increased bilirubin level in the blood by reducing the bilirubin levels.

What is an Rh factor screening test?

To know the Rh factor of a person, it is vital for a healthcare provider to conduct the Rh screening test. This test uses the blood sample to determine whether RBCs have the Rh antigen or not. The doctors may also find it feasible to recommend a prenatal test that can determine the Rh status of the baby during the pregnancy.

Rh-screening test is done if someone planning for a pregnancy, needs a blood transfusion, or want to donate blood.

Why is the Rh factor important during pregnancy?

Various complications that may arise during the pregnancy are unpredictable. Sometimes, a woman’s body acts in unexpected ways, and it could compromise both the health of the mother and the baby during gestation.

However, the doctor might be able to predict certain complications successfully. One such complication is the baby’s Rh factor.

If one considers becoming pregnant, an expert may suggest that the woman and her partner get a blood test to determine if both are Rh-positive and negative. The test may provide vital information about the Rh proteins attached to the blood cells. Until one is pregnant, the positivity or negativity of the Rh antigens will not be a cause of concern.

If one does not have Rh proteins in their blood cells, they are Rh-negative.

The patient should consider that the antibodies produced aren’t an issue during the first pregnancy. The concern is with the woman’s subsequent pregnancy. If the next born is Rh-positive, these Rh antibodies may cross the placenta and damage the baby’s RBCs. 

It may lead to life-threatening Anaemia, a condition that destroys a baby’s red blood cells quicker than the body can replace them. If one is Rh-negative, they might need to take another blood test — an antibody screen — during the first trimester, during week 28 of pregnancy, and at delivery

The antibody screen helps detect antibodies to Rh-positive blood. Suppose the woman hasn’t started to produce Rh antibodies. In that case, the doctors may likely recommend an injection, Rh-immune globulin – for the immune system to prevent the body from producing Rh antibodies during pregnancy.

If the baby is born having Rh-negative, no additional treatment is needed. Although, if a baby is born Rh positive, the woman needs another injection shortly after the delivery.


As discussed above, if one is Rh-positive, no action is needed.

But if the person is Rh-negative and the baby is Rh-positive, there’s a potential for the body to produce antibodies that could be harmful during a subsequent pregnancy.

Knowing a person’s Rh factor is vital to understanding their blood compatibility.

This compatibility is particularly crucial to consider during pregnancy and blood transfusion. Severe cases of rhesus disease, if left untreated,  can lead to stillbirth. In other cases, it may lead to brain damage, blindness, hearing loss, learning difficulties and vision loss. But, treatment is generally effective, and these problems are rare.

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