Much of what will be said here refers to the knowledge mentioned in the last post, about blood.

The name ‘Rh’ is an acronym for ‘Rhesus factor’. This is because the first time scientists observed the Rh factor was during a blood analysis of Rhesus monkeys. Since then, we have discovered that Rhesus molecules are present in most life forms. Even some kind of bacteria carries Rh molecules.

The Rh factor has an ancient origin, descending from the Amt molecule, which is found in every living thing, including Archea, the oldest living organism on Earth.

Although Rh varies between species, they all have the same function. The similar DNA instructions they have are to carry and distribute gases within cells. The Amt do the same. They have a similar DNA to Rh molecules.

The Rh factor is almost like a simplified version of the dynamics behind blood types. There are two main options: your Rh factor can be either positive or negative.

As you probably remember, we all have two copies of almost all our genes, one from each parent. The RHD gene can have at least two versions: positive and negative. It’s easy to assume that two RHD+ genes will result in Rh+ blood. The same can be assumed with two Rh-.

If one parent gives you an Rh+ gene and the other gives you an Rh- gene, you will be an Rh+ carrier for Rh- blood. This is because people with just one RHD gene produce enough protein to be Rh+. If you are Rh-, neither of your RHD genes knows how to produce the RHD protein.

In simple terms, if you are Rh-, both of your parents must be carriers of the Rh- version of the RHD gene, which is fairly common.

If you are a woman intending to become pregnant, it is important to be aware of the possibility of Rh incompatibility during pregnancy. This can happen if the mother is Rh-. This wouldn’t affect the first pregnancy, but could lead to problems in subsequent pregnancies.

This is because, during birth, the blood of the mother and baby mixes. In an Rh- mother, her immune system is unable to recognise the Rh+ in the baby’s blood, so it will produce antibodies against it. This process takes time, so it will not be a problem for this pregnancy, but it will affect subsequent pregnancies.

Since the mother’s immune system will already have antibodies against Rh+, her body will see the baby as an intruder and attack any Rh+ cells in the unborn baby. This is called Rh disease of the newborn. But there’s no reason to be afraid, since if you need, you can take a couple of RhoGAM shots during pregnancy, that prevents the mother’s immune system from harming the unborn baby.

The RhoGAM’s function is to absorb all the Rh+ cells released from the baby, thereby preventing the mother’s body from mounting an immune response to them.