Rhesus Positive and Negative: What You Need To Know

Mark Wealth

The term “rhesus” was coined from the rhesus macaque monkey. Some scientists performed a blood transfusion experiment between the monkey and the rabbit and found out some interesting compatibility attributes of the monkey’s blood.

Some years and a few researches later, some other scientists found this same compatibility in a woman and in honour of the first scientists, they called the blood with this property the ‘Rhesus Factor’ or ‘Rh factor’.

The Rhesus Factor (Rh Positive)

The Rhesus factor actually refers to a type of blood group that has some type of protein on the surface of the red blood cells.

If an individual has the Rhesus Factor (let’s call it Rh factor from now on), he/she is said to be Rh positive (Rh+).

If the individual’s Red blood cells does not have that protein (Rh factor), he/she is Rh negative.

The Rh Drama

So what’s all the fuss about Rh positive and Rh negative? Is it a bad thing if one is Rh negative?

Well neither Rh positive or Rh negative is bad on its own, not until there is a pregnancy.

If both parents are Rh positive or negative, their child is going to be Rh positive or negative respectively.

If however, both parents have different Rh status, that is one parent is negative while the other is positive, their child will either be negative or positive.

Now this is where the problem is. If a mother is Rh negative and she gets pregnant with a baby that is Rh positive, her immune system will see the baby’s Rh positive blood as a harmful invader and will start producing antibodies that destroy the red blood cells. Here we can say the woman has become Rhesus sensitized.

The fetus blood could find its way to the woman’s blood system through the placenta if there are some abnormal events. The antibodies destroy the red blood cells of the fetus thereby reducing the baby’s oxygen supply.

The Wahala…

‘Wahala’ means trouble. A baby whose mother’s antibodies destroy his/her red blood cells is in danger of hemolytic anaemia.

Hemolytic anemia could lead to serious illness and sometimes, death. Note that although a woman can get Rh sensitized during her first pregnancy, the baby will usually be safe because the mother’s body won’t be able to produce antibodies fast enough to do any damage. Subsequent pregnancies won’t be that lucky though.

The Remedy/Relief

The situation is not hopeless though. Your doctor probably knows your Rhesus status and will probably run a blood test called an antibody screen during your first trimester. Also, when you are 28 weeks or 7 months along. This test is to determine if you have been sensitized and how many antibodies your body has produced.

If you haven’t been sensitised, you will be given a Rhesus immunoglobulin shot (RhIg) that targets Rh positive cells and prevents your body from seeing them as ‘bad guys’. The end result is that antibodies won’t be produced and Hemolytic anaemia will be prevented.

If, on the other hand, you have been sensitized, your baby will be monitored and a blood transfusion will have to be done through the umbilical cord otherwise, the baby will have to be delivered before time, say at thirty-seven weeks.

Then, you will have to take measures to ensure that your preterm baby gets what she missed out of until she’s well and good.

Do you know your Rhesus status? You should go and find out if you don’t. If you do, you can take steps to make sure it doesn’t cause any problems for baby and you.