WHAT BLOOD GROUP AND RH FACTOR WILL MY BABY INHERIT?

When the baby is born, a drop of blood is taken to know the blood group and the Rh factor that you inherited from your parents. It is not so easy to decipher it because it is not determined according to the combination of groups that parents have, so we will explain in a simple way some genetic laws that will help us to know what type of blood group and Rh factor can the baby inherit.

Often, the baby's blood group may be surprising since it does not correspond to any of his parents, but it will depend on the genetic information he inherits from each of them, since each person has two alleles from his father and his mother.

Blood groups

A blood group is a classification of the blood according to the characteristics present in the red blood cells and in the blood serum. The two most important classifications in humans are the antigens (A, B, O) and the Rh factor.

In Babies and more, what is Rh incompatibility?

There are some basic notions of genetics that we must know to better understand the inheritance of blood groups:

The gene that determines the blood group has three variants or alleles: A, B and O that give rise to four blood groups: A, B, O or AB.
Each human being inherits genes from the father and mother, but in turn each of them has dominant and recessive genes. Each person has two alleles, coming from his father and his mother. That is, even if the blood group is A, B, O or AB, the person will have a combination of genes that can be AA, AO, AB, OO, BB and BO.
The genes A and B are dominant and gene 0 is recessive, for example:
- A person with group AB has a gene A and another B.
- A person with group A can be AA or A0, but the dominant A gene prevails.
- A person with group B can be BB or B0, but the dominant B gene prevails.
- A person with group 0 has both 0 genes.

What blood group will the baby have?

As explained above, we can see that the inheritance of the blood group is not as simple as knowing the groups of the parents.

Each parent will give their child one of their two alleles. Possible combinations between the four inheritable alleles (two from the father and two from the mother) they give us 16 possibilities, which will determine the inherited group. For example:

PARENT GROUP A:
- Mother Group A: son Group A or 0
- Mother Group B: son Group 0, A, B or AB
- Mother Group AB: son Group A, B or AB
- Mother Group 0: child Group A or 0
FATHER GROUP B:
- Mother Group A: son Group 0, A, B or AB
- Mother Group B: son Group B or 0
- Mother Group AB: son Group A, B or AB
- Mother Group 0: son Group B or 0
FATHER GROUP AB:
- Mother Group A: son Group A, B or AB
- Mother Group B: son Group A, B or AB
- Mother Group AB: son Group A, B or AB
- Mother Group 0: child Group A or B
GROUP FATHER 0:
- Mother Group A: son Group A or 0
- Mother Group B: son Group B or 0
- Mother Group AB: son Group A or B
- Mother Group 0: son Group 0

In Babies and more Rh incompatibility and pregnancy hazards

Recall that one allele of the gene that determines the blood group is inherited from the father and the other from the mother, but they, in turn, will be able to randomly transmit, one of the two alleles they have in their genetic endowment, which will be represented in the gamete, ovum and sperm. For that reason children of the same partner may have different blood groups, depending on the allele transmitted by each parent.

The combinations give rise to different examples of inheritance of blood groups according to the way in which this inheritance occurs.

What Rh factor will the baby have?

In addition to blood groups, all people have a positive or negative Rh factor Depending on the characteristics of your blood.

Rh of the blood is determined by an antigen found on the surface of red blood cells or also known as red blood cells. These are the most common type of cells that are found in the blood and that are the main source for transporting the oxygen necessary for our body. We are Rh positive if the antigen is in our blood and Rh negative if we do not have it.

In Babies and more, what blood group will my child have?

Rh inheritance consists of two genes, one is inherited from the mother and the other from the father and follows a common pattern. Rh positive gene is dominant, that is to say that even when combined with an Rh negative gene, the positive prevails. Therefore, most people (85%) are Rh positive.

If a person has the genes + +, the Rh factor in the baby's blood will be positive.
If a person has the genes + - , the Rh factor in the baby's blood will be positive.
If a person has the genes - - , the Rh factor in the baby's blood will be negative.

Inheritance of Rh Factor:

MOTHER Rh-:
- Father Rh-: son Rh-
- Father Rh + (++): son Rh +
- Father Rh + (+ -): son Rh + or Rh-
MOTHER Rh + (++), in parentheses alleles inherited from parents:
- Father Rh-: son Rh + or Rh-
- Father Rh + (++): son Rh +
- Father Rh + (+ -): son Rh + or Rh-
MOTHER Rh + (+ -):
- Father Rh-: son Rh + or Rh-
- Father Rh + (++): son Rh +
- Father Rh + (+ -): son Rh + or Rh-

Rh factor inheritance probabilities

As we see, there are nine possibilities of genetic inheritance of Rh factor which give rise to different probabilities, as the case may be:

However, about Rh incompatibility or Rh sensitization, this can only occur when the mother is Rh negative factor and the Rh positive father (cases 4 and 7). If the baby inherits the Rh positive factor from the father, hemolytic disease of the newborn occurs. The mother's immune system can "attack" the Rh-positive red blood cells of the fetus causing anemia, jaundice and even fetal death. We have already detailed all this extensively when we explained what Rh incompatibility is.