Blood compatibility between a mother and a father is particularly monitored during pregnancy. What are the risks in the event of Rhesus incompatibility? Why are pregnant women, who already have a child, more affected by fetal-maternal incompatibility? Answers from Léa Marchal, midwife.
Some rhesus are not compatible with each other. In a couple, on a daily basis, this inadequacy has no impact but it poses a problem when a baby project materializes. Rhesus incompatibility intervenes when the mother has a negative rhesus, and baby is positive as her father. The mother’s immune system then sets in motion to create anti-Rhesus anti-corps at the time of the second pregnancy. Here is why.
What is Rhesus incompatibility?
Behind this term hide a lot of anxieties and questions for future parents. However, prevention makes it possible to limit very effectively The risks for the baby. During a pregnancy, the search for Mother’s blood group is one of the compulsory examinations of the first quarter, for two reasons. The first, to be able to practice a Transfusion of “compatible blood“The second, to know if the mother and the child are not” incompatible “. Indeed, a negative rhesus in contact with a positive rhesus Protects and manufactures anti-Rhesus antibodies, agglutinins, destructive red blood cells carrying this rhesus. Thus, the mother’s immune system could endanger the fetus and cause more or less serious accidents (anemia, brain sequelae …). To help you better understand what is Rhesus incompatibilitywe take stock of the blood groups and the different situations between the rhesus of the mother and the dad.
A blood group includes a letter A, B or O and a sign + or -. Rhesus is a genetic particularity: we are always the same rhesus whether it is positive or negative. The sign + or – corresponds to the rhesus.
- One person is positive rhesus (+) If its red blood cells carry, on their surface, a certain molecule, called rhesus molecule.
- One person is negative rhesus If its red blood cells do not relate to their rhesus molecule surface.
- A woman rhesus negative pregnant of a positive rhesus man can give birth to a positive rhesus child.
Rhesususus-maternal incompatibility: what are the risks?
Only couples whose The woman is negative rhesus and the rhesus man positive (and not the opposite!) Will be the subject of close monitoring. Indeed, their baby has one in two chance of inheriting his father’s positive rhesus and therefore running a risk. There is therefore no risk of fetal incompatibility between:
- a rhesus + mother, a rhesus + father and a child rhesus + or –
- A mother rhesus +, a rhesus father – and a child rhesus + or –
- A rhesus mother -, a rhesus father – and a rhesus child –
- A rhesus mother -, a rhesus + father and a rhesus child -.
Nevertheless, A risk of fetal incompatibility exists when the mother is rhesus -, the father rhesus + and the child rhesus +.
Rhesus fetal-maternal incompatibility: what risks during the first pregnancy?
“There is no no risk during the first pregnancy, But you have to perform a Rhesus prevention When you are negative rhesus so as not to be immunized against positive rhesus embryos “ explains Léa Marchal, midwife. During a first delivery (or an FCS or FCT or abortion): red blood cells or positive rhesus embryo can pass through maternal blood. The mother then manufactures anti-Rhesus antibodiescalled irregular agglutinins. “She will then immunize against the embryos/fetus of positive rhesus” specifies the midwife.
Second pregnancy and negative rhesus: What does it change?
When a mother of negative rhesus gives birth to his 2nd child rhesus positive And that his partner is also positive, you have to pay attention to Rhesus incompatibility. Immunization is most often carried out at the time of childbirth. The risk occurs during a next pregnancy, even if the first was not completed, either because of a miscarriage, or because of a voluntary termination of pregnancy. If the embryo or fetus is still rhesus positive, maternal anti-Rhesususus antibodies can cross the placenta and attack the red blood cells of the fetus.
Rhesus fetal-maternal incompatibility: what risks for the fetus?
The passage of maternal antibodies in fetal blood can cause anemia, edema, jaundice or brain damage.
Rhesus fetal-maternal incompatibility: what treatments?
In the event of incompatibility, We will verify by blood test that the maternal reaction against the baby’s globules did not start despite the precautions. 72 hours after childbirth, an injection of antibodies is carried out allowing Neutralize the Rhesus positive red blood cells of the fetus/babybefore the mother developed antibodies.“This same injection can also be administered during pregnancy at around 28 weeks of amenorrhea. The injection is systematic for women of negative rhesus, except cases where we are certain that the fetus is negative rhesus” Recalls Léa Marchal. The injection is also carried out whenever there is a possibility of contact between the baby’s blood and that of the mother, during a surgical operation for example, an amniocentesis, or a blood test, an abdominal trauma.
The treatment will then depend on the degree of anemia of the child. As Léa Marchal explains: “The child may only need intensive phototherapy. It is then placed under a blue light ramp which eliminates the bilirubin at the origin of the newborn jaundice.“In serious cases of Allo-Immunization Rhesus, fortunately rarer, when anemia is very severe: “We can perform a blood transfusion and replace the child’s blood by exsanguino-transfusion.”
Thanks to Léa Marchal, midwife.
