Pregnancy and negative Blood group. Why your blood group is essential to know when you are pregnant?

Is your blood group is either one of the following?

• A negative
• B negative
• AB negative
• O negative

Are you pregnant? Then you have something to worry about.

Everybody’s blood group follows either ‘positive’ or ‘negative’. What does this means. Positive means the presence of a special kind of antigen on the surface of the red blood cell, and negative means its absence.

More confused? Well let me try to explain further. Our body is composed of various molecules. Each and every one of these molecules is determined by genes. I guess you know what genes are. They are parts of our genome which carry the coding for these molecules. If you have the gene your body can produce the molecule. If not you can’t. It is simple, isn’t if?

Now back to blood groups. As mentioned above there is gene called the gene D.  This is responsible for the formation of the rhesus antigen on the surface of the red blood cells. So the negative people don’t have that gene and therefore, they don’t have the antigen on the surface of the red blood cells.

I have used the word ‘antigen’. What does this mean? An antigen is a any molecule that is foreign to our body.

What does this have to do with pregnancy?

Well, the problem comes when a negative mother is carrying a positive fetus for the first time in her life. As described above the positive baby has the antigen in their blood cells. Now, during delivery, the child’s blood mixes with the mother’s blood. So the mother’s body recognizes the antigen in red cells from the fetus and produces antibody against them.

These antibodies go and attack red cells with that antigen and destroy them. The first child is not affected. The problem comes when the mother is conceiving for the second time with a positive fetus. Now the mother’s body has preformed antigens, which can enter the fetal blood stream, and attack fetal red blood cells.

This leads to rapid destruction of fetal blood cells and thereby leads to fetal anemia and hydrops fetalis.  

If you have any query, just leave it on comments, I am always looking forward to answer them all.