RH Incompatibility in Pregnancy

When an Rh negative woman becomes pregnant, if the father is Rh positive, the fetus can be negative like the mother or positive like the father, this is called Rh incompatibility.

The red blood cells of our blood have characteristics that are specific to each individual, which we call the Blood Group . The most important correspond to groups A, B or 0 and Rh. These groups and Rh are inherited and are a combination of those of our father and our mother.

What about the Rh?

Specifically , Rh can be positive or negative and this means that Rh positive people have a special mark on the surface of each of their red blood cells that Rh negative people lack.

Rh-positive people can receive an Rh-negative blood transfusion , because the red blood cells are like yours without that identification card on their surface, so far no problem. However, it cannot be done the other way around : if we put an Rh negative individual in contact with these marked red blood cells, which express an identification that they do not have, they will recognize them as something foreign and will generate antibodies destined to destroy each of the labeled blood cells they find. In our environment practically 85% of the population is Rh positive and only 15% negative. The contact can be due to a poorly chosen blood transfusion, due to the exchange of syringes… All these situations must be avoided. And also in pregnancy…

And what happens in pregnancy?

When an Rh negative woman becomes pregnant, if the father is Rh positive , the fetus can be negative like the mother or positive like the father, this is called Rh incompatibility . During the course of normal pregnancy there should be no problem if the mother has never previously been in contact with Rh-positive blood because the blood of the fetus and the mother do not come into contact, but there are situations in which this contact can occur: some bleeding during pregnancy, invasive technique such as amniocentesis or chorionic biopsy, abortion or ectopic pregnancy, or during childbirth. When this happens, the Rh negative mother initiates this reaction and the pregnant woman is permanently immunized against Rh positive blood, this is called Rh isoimmunization . In the current pregnancy there is no time for the reaction to be serious, the problem will be in subsequent pregnancies , since from the early stages of pregnancy those antibodies present in the maternal blood will be dedicated to destroying the fetal red blood cells causing a picture of fetal anemia and a complex syndrome that can have severe consequences called Neonatal Hemolytic Disease.

It can be avoided?

Yes! In a very simple way, administering to the pregnant woman a dose of those same antibodies that she could generate , thus tricking her immune system, which trusts itself, as if someone had done its job and thus it is no longer necessary for it to generate its own antibodies against labeled red blood cells.

When is it necessary to do it?

In each situation that may favor fetal blood contact with maternal blood, this medication, called anti-D gamma globulin, must be administered.

  • In major bleeding in the first trimester
  • Post abortion or ectopic pregnancy
  • Post amniocentesis or chorion biopsy.
  • Also in a protocolized way at week 28 of pregnancy.

In all these situations we do it without knowing the fetal Rh, which if it is negative like the mother’s would not be necessary, but it would not be harmful either. In the postpartum period, we do know the Rh of the newborn , since a sample of blood from the umbilical cord is always taken and the blood group is analyzed. In this case, gamma globulin is only administered when the baby is Rh positive.

If this precaution has not been taken, we will detect maternal antibodies, which are requested in the analysis of each trimester of pregnancy from all pregnant women through a simple blood test called the Coombs Test . In case of positivity and hemolytic disease, we will study if there is fetal anemia and its degree by means of Doppler ultrasound. In severe cases it may be necessary to transfuse the fetus inside the uterus until it is viable and can be removed, which is why it is so important to administer postpartum gamma globulin when necessary.

With this simple measure, since it has been carried out systematically since the 1960s, this pathology has almost completely disappeared in developed countries, which at that time caused the death of 48 out of every 100,000 newborns.

WHAT YOU SHOULD KNOW…

  • When an Rh negative woman becomes pregnant, if the father is Rh positive, the fetus can be negative like the mother or positive like the father, this is called Rh incompatibility.
  • In a normal pregnancy there should be no problem if the mother has never previously been in contact with Rh-positive blood because the blood of the fetus and the mother do not come into contact, but there are situations in which there can be such contact and then it’s time to act
  • In each situation that may favor contact of fetal blood with maternal blood, this medication, called anti-D gamma globulin, must be administered.
Leave a Reply

Your email address will not be published.