Rh intolerance: causes and consequences

If a pregnant woman is rhesus-negative, a little caution is required, as this could lead to rhesus intolerance between mother and child. Although this is relatively harmless in the first pregnancy, it can unfortunately lead to serious damage to the baby in subsequent pregnancies.

Luckily, nowadays the antibody screening test helps to reliably diagnose Rhesus intolerance. The administration of the so-called rhesus prophylaxis ensures that there are no problems even with several pregnancies.

What is the rhesus factor?

Rhesus factors are characteristics of the blood groups, more precisely of the red blood cells. In about 85 percent of people, the red blood cells carry certain proteins. They are classified as Rhesus positive. The remaining 15 percent of people do not have these proteins, so they are referred to as Rh negative.

Figure: Formation of a rhesus intolerance

How does Rhesus intolerance come about?

  • Rh intolerance can usually only occur if you are rhesus negative and your baby is rhesus positive. So it requires that your partner is Rhesus-positive, because only then can your child “inherit” a positive Rhesus factor. In every other case (you are rhesus positive or your baby is rhesus negative), the rhesus factor has no effect and rhesus intolerance is virtually impossible.
  • In most cases, rhesus intolerance only affects a second pregnancy . Because in the case of a first-time mother, the mother’s blood circulation is almost always unaffected until the birth. The firstborn child is born healthy.
  • In most cases, the child’s red blood cells do not enter the maternal bloodstream until birth . Even the smallest amounts are sufficient to trigger antibody formation. The mother’s immune system stores this reaction for the future. In rare cases, however, a previous miscarriage, an abortion or an invasive procedure during pregnancy (e.g. an amniotic fluid test ) can also lead to the child’s red blood cells mixing with the mother’s blood.
  • If there is another pregnancy in which the child is rhesus-positive again, the rhesus intolerance is now having an effect . The mother’s immune system remembers and forms antibodies more quickly when it comes into contact with Rhesus-positive blood again. The mother’s antibodies travel across the placenta into the child’s bloodstream and try to destroy the “foreign” red blood cells. If the child’s organism cannot compensate for the destroyed red blood cells by forming new blood, this can lead to anemia , jaundice , water retention and finally, in the worst case, death of the child.

Rhesus prophylaxis (anti-D immunoglobulin) prevents

In order to prevent a rhesus intolerance from developing in the first place, your doctor will give you an anti-D-immunoglobalin injection in the 28th and 40th week of pregnancy (or directly after the birth) as a so-called rhesus prophylaxis. If you use an invasive diagnostic method, such as amniocentesis or chorionic villus sampling, then you will be given the prophylaxis after this procedure. Even the smallest amounts of blood could have entered your bloodstream. The active ingredient immediately kills the child’s rhesus-positive blood cells that have entered your bloodstream. It recognizes the antibodies supplied from outside, “relies” on their work and therefore does not form any antibodies of its own. The external antibodies are quickly broken down by your body. If you get pregnant again, there will be no more antibodies in your body. To be sure that you are given these shots, you should inform any doctor treating you that you are rhesus negative.

How do you determine a possible Rh intolerance?

During the initial examination , your doctor determines your blood group and your Rhesus factor. Your doctor will not rely on your information about your blood group, but will check it with a blood test in any case. If you are rhesus negative, your doctor will recommend rhesus prophylaxis and carry out regular antibody screening tests on you. They can already detect the smallest amounts of antibodies and therefore allow early intervention. During the ultrasound examinations , more attention is paid to abnormalities in the child’s development. For example, enlargement of the spleen or liver can indicate Rh intolerance. If the antibody search test or the ultrasound provide the first clues, aAmniocentesis provide more information about a possible risk to the unborn child. In particular, the bilurubin content of the amniotic fluid is checked. It indicates anemia. After the birth, the blood from the umbilical cord is tested again in order to be able to give the baby a blood transfusion directly if it is anemic. If necessary, a blood transfusion can be given before the baby is born. If the child is only diagnosed with slight anemia or jaundice, light therapy after birth is usually sufficient.

Symptoms and treatment of the child

If, despite the prophylaxis, Rhesus intolerance occurs, it manifests itself in the child as anemia. The mother’s antibodies kill the child’s red blood cells. The child’s organism reacts with increased blood production to compensate. In response, organs such as the liver and spleen enlarge.

Anemia is also evident after birth in the severe paleness of the child. Due to the destruction of the red blood cells, more bilirubin enters the child’s blood. Eyes and body turn yellow. One speaks of a childish “jaundice”.

If there is a further increase in bilirubin in the blood before birth, this is deposited in the child’s brain. It can then lead to serious damage to the child.

Because the red blood cells carry oxygen in the blood, destroying them reduces the baby’s oxygen supply.

The most serious consequence of anemia can be a large accumulation of fluid in different parts of the child’s body. It is called hydrops fetalis. This also leads to edema in important body cavities such as the pericardium. Unfortunately, these cases can result in miscarriage or death of the baby.

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