Rh sensitization during pregnancy

, medical expert
Last reviewed: 20.11.2021

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What is rhesus - sensitization during pregnancy?

The doctor diagnoses "rhesus-sensitization", when the mother's bloodstream reveals Rh-antibody. Rhesus antibodies are compounds of the protein structure that are produced in the maternal organism in response to the entry of Rh-positive fetal erythrocytes into it (the immune system of the expectant mother perceives these erythrocytes as alien).

The causes of rhesus - sensitization during pregnancy

Rhesus sensitization is observed during pregnancy, if the mother has a negative Rh factor of blood, and the fetus has a positive Rh factor. In most cases, the mother's blood does not mix with the blood of the fetus until the very birth. Antibodies that affect the fetus are formed over time and may not be observed during the first pregnancy. During the next pregnancy, when the fetus again has a positive Rh factor, the antibody is already present in the blood and begin to attack the fetus. As a result, the fetus develops anemia, jaundice or more serious diseases. This is called Rh disease. The condition worsens with every subsequent pregnancy, when the mother and child have different Rh factors.

During the first pregnancy, the fetus may develop Rh disease if the mother has been sensitized before or during the previous pregnancy. This can also occur in the case of:

  • Miscarriage, abortion or ectopic pregnancy and you did not get immunoglobulin to avoid sensitization.
  • Serious injury to the abdominal cavity during pregnancy.
  • You were given an amniocentesis or a biopsy of the chorionic villi in pregnancy and you were not given immunoglobulin. During such tests, the blood of the mother and the child may be mixed.

Sensitization is a very important factor that must be discussed with a doctor in the first trimester of pregnancy. Sensitization does not provoke any alarming symptoms, and it can be detected only by a blood test.

  • If you are at risk, rhesus sensitization is almost always preventable.
  • If you are already sensitized, you need to undergo a course of treatment to protect the health of the child.

Who is prone to sensitization during pregnancy?

Rhesus - sensitization during pregnancy can occur only if the mother has a negative Rh, and the child has a positive Rh.

If the mother has a negative Rhesus blood, and the father has a positive blood, there is a high probability that the child will be the same as that of the father. In a consequence, there can be a rhesus - conflict.

If both parents have Rh negative, the child will have the same. In such a situation, rhesus - there can be no conflict.

If you have a negative blood Rhesus, for safety reasons the doctor will prescribe a course of treatment, regardless of the blood type of the father.

Diagnosis of Rh-sensitization

All pregnant women are given a blood test during their first prenatal examination. His result will show a negative rhesus blood sensitization of the mother.

If you have a negative Rhesus blood, but you are not sensitized:

  • A repeat blood test can be scheduled between 24 and 28 weeks of gestation. If the results of the analysis confirm the fact that you are not sensitized, you may not need to do an additional antibody test before giving birth. (The probability of reanalysis in the case of a pregnant woman amniocentesis for 40 weeks of pregnancy or with placenta detachment, which caused uterine bleeding, is not excluded).
  • The newborn will be given a blood test after birth. If he has a positive Rhesus blood, you will need to take an antibody test to find out if you were sensitized at the end of the third trimester of pregnancy or during childbirth.

If you are sensitized, the doctor will closely monitor the course of your pregnancy, namely:

  • regularly check the level of antibodies in the blood;
  • conduct an ultrasound Doppler study to determine the flow of blood to the brain of the child, while anemia can be detected and the degree of the disease is determined.

Prevention of Rh-sensitization

If you have a negative Rhesus blood, but you are not sensitized, the doctor will give you several doses of immunoglobulin. Its administration is effective in 99 cases out of 100.

Immunoglobulin is administered:

  • in the case of a pregnant woman amniocentesis;
  • at 28 weeks of gestation;
  • after childbirth, if the child has a positive Rhesus blood.

The drug helps only for a certain time, so you should take a course of treatment with each pregnancy. (To avoid sensitization in repeated pregnancies, immunoglobulin is administered to women with negative blood rhesus in case of miscarriage, abortion or ectopic pregnancy).

Injections will not benefit if you are already sensitized.


If you are sensitized, the doctor during pregnancy will conduct regular testing, in order to determine the state of the health of the fetus. It should also go to the reception to the perinatologist.

The course of treatment of a child depends on the severity of anemia.

  • If there is a mild form of anemia, you will have to take additional tests during pregnancy.
  • If the disease worsens, the only correct solution is premature removal of the child. After birth, some newborns may need a blood transfusion or treatment of jaundice.
  • In case of severe anemia, the child is given a blood transfusion in the womb. This will help to protect his health and will give him additional time for full maturation. In most of these cases, during the delivery, a caesarean section and additional blood transfusion are done immediately after childbirth.

In the past, sensitization often led to the death of a child. But modern testing and treatment allow such children to safely be born and normally develop in the future.

Causes of Rh-sensitization during pregnancy

Rhesus - sensitization occurs when a woman with negative rhesus is exposed to positive rhesus. About 90% of parturients are sensitized during labor because their blood mixes with the blood of the child. Later, the immune system of women begins the production of antibodies against Rhesus - positive erythrocytes.

Experts do not know how much blood causes sensitization during labor. But many women are sensitized during pregnancy or labor, even if 0.1 ml of Rh-positive fetal blood enters their bloodstream. Fortunately, avoiding a rhesus-conflict is possible by introducing an immunoglobulin into the mother's body.

When the immune system of a woman undergoes sensitization for the first time, it takes several weeks to produce immunoglobulin M or antibodies. The antibodies are too large to get into the placenta, so the Rh-positive fetus does not cause any harm. The pre-sensitized immune system reacts quickly to Rh-positive blood, as it was during the second pregnancy with a Rh-positive fetus. Usually, just hours after exposure to blood with a positive rhesus, immunoglobulin G is produced. These antibodies are passed through the placenta to the fetus and destroy its erythrocytes. There is a rhesus-conflict, which is dangerous for the future child.

Some Rhesus negative people are never sensitized, even in the case of exposure to a large amount of blood with positive rhesus. The reason for this is not yet known.

trusted-source[1], [2], [3]

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