Rh incompatibility in pregnancy

23 August, 2021

Escrito por el equipo médico fivmadrid

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Have you heard about Rh incompatibility? One of the first steps when confirming pregnancy is a blood test. Among other aspects, this test allows to know the woman’s blood group, as well as her Rh factor. The reason for determining it is due to the relevance that it can take on the health of the baby during pregnancy, and that is why it is important to determine it as soon as possible.


The Rh factor is a protein present in some red blood cells. Although most of us have this factor in our blood, it is worth noting that it does not occur in 100% of cases. This is what determines whether the factor is positive or negative. If the protein is present in the blood, we are talking about a person with Rh positive (Rh +) and, otherwise, Rh negative (Rh-).


Rh incompatibility occurs when both parents do not share the same factor. That is, it occurs when the parents have opposite blood groups according to the Rh factor. In these cases, there is a 50% chance that the future baby will inherit the factor from her mother and a 50% chance from the father.


It is important to note that this is not usually a problem, especially if it is the woman’s first pregnancy. It is because during the first pregnancy, the baby’s blood does not usually come into contact with the mother’s circulatory system.


When can this become a problem?


The potential problem would occur at the time of delivery, under very specific conditions. First, the mother would have to have an Rh- factor and her baby Rh +. It is possible that the mother’s blood and her child mix during this process and, if it occurs, the woman’s body could develop antibodies against the Rh protein, detecting it as an external agent.


Other ways in which an Rh negative woman could develop these antibodies could be due to Rh positive blood transfusion, miscarriages, and ectopic pregnancies.


These antibodies would be completely harmless to the mother. However, if the mother were to become pregnant again with a factor-positive baby, these antibodies would recognize the Rh + protein in the baby’s red blood cells as foreign substances, and could attack the cells that contain it. When this happens, the baby is diagnosed with hemolytic disease or Rh disease, the main consequence of which would be a very low rate of red blood cells.


Rh incompatibility should not become a concern, as there is a simple treatment that prevents complications in pregnancy, childbirth and the health of the newborn. If a mother is likely to develop this condition, she is given two injections of Rh immune globulin; one around the 28th week of gestation and the last one around 72 hours before giving birth.


The effect of immunoglobulin in the mother acts as a vaccine, and prevents the body from making antibodies against Rh, thus eliminating the possibility of affecting the baby’s health.

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