What you need to know about Rhesus Factor

Rhesus factor is a type of protein fixed by your genes found on the surface of red blood cells. Rhesus-positive means a protein, D-antigen is found on the surface of your red blood cells, and if you do not have the D-antigen protein, then you are Rhesus-negative.

How do I know if I am Rh-negative or Rh-positive?

Through blood tests, if your blood contains the D-antigen, then you are Rh-positive, otherwise, you are Rh-negative. Most people, about 85% are rhesus positive.

There are matching issues with Rhesus factor that comes up during pregnancy when the mother is rhesus-negative and the fetus is rhesus-positive, the fetus most likely inherited it from his/her daddy.

Problems may arise if some of the fetus’ blood enters your bloodstream, the immune system of the mother will react to the D-antigen present in the baby’s blood and treat it as a foreign body. To fight it, the mother’s body produces antibodies against it. This is known as sensitizing, and it occurs every time the fetus’ blood mixes with the mother’s.


Studies show that this may not be harmful in the first pregnancy. However, it poses a serious threat to the life of the baby when the mother is pregnant again with a rhesus-positive baby. The antibodies produced by your body the first time has the capacity to rapidly multiply, cross the placenta and then attack the blood cells of the fetus causing a disease known as Rhesus disease. This Rhesus disease can attack the child during and even few months after the pregnancy, it allows for a breakdown of the fetus’ red blood cells causing a condition known as hemolytic anemia which can lead to severe life-threatening health conditions such as heart failure, illness, brain damage.

Any hope?

Yes! Fortunately, An injection known as anti-D immunoglobin(RhIg) can be administered at intervals during and few months after delivery to guard against the harmful effects of these antibodies. Once you realize you are pregnant, it is advisable that as part of your antenatal care, a blood test is conducted to determine your blood group and Rh-factor and appropriate steps are taken to safeguard your life and that of your baby.