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What is Rh factor incompatibility?

Maria Fernanda
5 min read

Rh factor incompatibility represents a cause of neonatal hospitalization with a high mortality rate.

For this reason, it is important to make a timely diagnosis, in order to reduce the risk of death.

What is the Rh factor?

In red blood cells (erythrocytes), there are a series of antigens, which have the function of identifying the type of blood that each person has, that is, if it belongs to group O, A, B or AB.

In the same way, it happens with the Rh factor, this refers to the blood type system, if it is Rh positive or Rh negative.

If you did not know, there are up to six types of Rh antigen, whose name is assigned with a letter, either C, D or E.

What is Rh factor incompatibility? – Wellness and Health – WebMediums
Rh factor incompatibility

On the other hand, of these three, the one that has the greatest effect as an antigen is D, apart from being the most frequent in the world population.

In this sense, if a person has the D antigen on their surface, their blood type is classified as Rh positive, while if they do not have it, then they are Rh negative.

It is important to mention that although a person does not have the antigen expressed in red blood cells, it does not mean that they are not prone to developing a reaction during a transfusion.

What is the difference between blood group antigens and Rh factor?

The difference is that blood groups O, A and B cause serious antigen-antibody reactions, they are responsible more than anything for an acute process.

Unlike the Rh antigen where the reaction does not appear quickly, but requires intense exposure to the antigen.

What is Rh factor incompatibility?

Previously, it was known as erythroblastosis fetalis or hemolytic disease of the newborn. It consists of the agglutination of red blood cells in the fetus and in the newborn.

This pathology causes unconjugated hyperbilirubinemia, which means that the blood levels of bilirubin increase and that the origin is not in the liver.

Why does Rh incompatibility occur?

Incompatibility is more common in the context of an Rh negative mother and a father with Rh positive blood. Usually, the blood that the fetus inherits is Rh positive.

The problem occurs when there is a maternal exposure of the fetus's blood.

What is Rh factor incompatibility? – Wellness and Health – WebMediums
Maternal exposure

As a result, the mother's body recognizes the D antigen as foreign, so that the mother becomes "sensitized" and her body begins to produce anti-D antibodies.

Anti-D antigens travel to the fetal circulation, generating an antigen-antibody reaction, destroying fetal red blood cells.

Anti-D IgM and IgG antibodies

Immunoglobulins (IgM and IgG) are the type of anti-D antibodies that the mother makes.

An interesting fact is that the first exposure of the mother to the D antigen will generate IgM-type antibodies.

The advantage of this type of immune globulin is that it cannot cross the placenta as easily, so there is no significant risk with the first pregnancy.

However, in subsequent pregnancies, these antibodies are no longer IgM, but IgG. The latter can cross the placental barrier.

Why does the incompatibility not affect the first child with an Rh positive blood type?

It does not mean that it is not affected, only that the literatures report that the probability exists, but it is 1%. It should be noted that this probability increases with each pregnancy.

The reason for this has to do with the aforementioned. In addition to this, during the first pregnancy the amount of fetal red blood cells that are in contact with the mother's blood is low.

What is Rh factor incompatibility? – Wellness and Health – WebMediums
Rh positive first child

Likewise, the time when there is greater exposure is in childbirth, the consequence is maternal sensitization.

Sensitization causes that a new exposure to the D antigen, your body produces more anti-D antibodies.

Effects of maternal antibodies on the fetus

The consequence is fetal hemolysis, which depends on the degree of exposure. In simpler words, the fetus begins to suffer from anemia from destruction of the red blood cell.

Subsequently, hemolysis results in hyperbilirubinemia.

However, it is unlikely that the child will be born yellow due to bilirubin, since the elimination of the waste is carried out by the placenta.

Anemia is a very serious condition in the fetus, causing death in the uterus. Besides, it can be classified as follows.

  • Mild hemolytic disease. Luckily, it is the most common and anemia is not alarming.

  • Moderate hemolytic disease. Its incidence is infrequent and the newborn's hemoglobin is <14 g / dL.

  • Severe hemolytic disease. In this type, newborns die in utero.

When to put the Immunoglobulin RhoGAM?

Have you heard about RhoGAM immunoglobulin? It is an injection that must be administered to all Rh negative mothers and the baby's father is Rh positive, even if the type of blood system is unknown.

This injection is important because the risk of a factor incompatibility is reduced.

What is Rh factor incompatibility? – Wellness and Health – WebMediums
RhoGAM injection

Now, the opportune moment to place the injection depends on the health center, but in general it is indicated in the following circumstance.

  • Rh negative mother who is not sensitized, immunoglobulin should be placed at 28 weeks of gestation.

  • The second dose should be given within 72 hours after delivery, but only if the child is Rh positive.

What are the benefits of taking the immunoglobulin RhoGAM?

  • Prevents hemolytic disease of the newborn.

  • Possibly protects the fetus from anemia. As well as neurological alterations.

  • Lowers the likelihood of heart failure.

Risk of RhoGAM Immunoglobulin Placement

Some of the risks that may appear are.

  • Pain in the injection area.

  • Allergic reaction to immunoglobulin.

  • Headache, nausea, vomiting, and dizziness.

In the presence of some of these symptoms you should go to a health center for a medical evaluation.