THE RHESUS FACTOR- And how it affects your pregnancy

Many people become confused when the term Rhesus factor is brought up. The Rhesus factor refers to the availability or lack of a protein (D antigen) found on the surface

  • PublishedApril 8, 2019

Many people become confused when the term Rhesus factor is brought up. The Rhesus factor refers to the availability or lack of a protein (D antigen) found on the surface of the red blood cells.

If one has it, then they’re deemed to be Rhesus positive or RhD positive. If you don’t have it, then you are deemed as Rhesus negative or RhD negative.

The Rhesus factor is genetically defined or fixed so there is nothing you can do about it. It also helps to give one their blood group identity, that is, whether your blood group is positive or negative.

Generally speaking, there is nothing inherently wrong with being Rhesus positive or negative but in pregnancy, it can be lethal due to a phenomenon known as Rhesus incompatibility. Rhesus incompatibility usually happens if a mother’s blood group is Rhesus negative and their partner is Rhesus positive. This means there’s a 50 per cent chance that your child may be Rhesus positive and herein lays the danger.

If your baby’s Rhesus positive blood mixes with your Rhesus negative blood, your bloodstream adversely reacts to the D antigen. This is because the D antigen is identified and treated as a foreign invader. Your body then produces antibodies to fight the protein, in a process known as sensitising, which is basically your body forming a memory of the nature of the ‘invader’ and the intended action to take.

While this process may not affect your first-born child, it can put your future offspring in danger. Should your next child be Rhesus positive, it is likely your body will identify the D antigen as an invader and the antibodies created during the initial sensitising process can quickly multiply, cross over into the placenta and attack your baby’s blood cells. This condition can lead to stillbirths and in the event that your child does survive, the antibodies can continue with the attack even post birth.

This results in what medics refer to as Rhesus disease or haemolytic disease of the foetus and newborn (HDFN). This disease causes the baby to be anaemic or jaundiced, usually characterised by yellow pigmentation on the child’s skin, bilirubin, produced from broken down red blood cells. Severe cases of jaundice may lead to:

Adverse effects on baby’s brain cells causing the baby to be less active

1. Brain damage
2. Seizures and convulsions
3. Deafness, cerebral palsy

Treating the condition

If you are sensitised, doctors will administer an anti-D injection known as anti D immunoglobulin which kills any foetal blood cells in your circulation before antibodies are formed (sensitisation) hence stopping any attack.

Remember, once the anti-D antibodies are formed, they stay in your blood forever hence why the anti-D immunoglobulin can ONLY be administered before both bloods mix. The injection is administered to the mother during 28th and 34th week of pregnancy and within 72 hours once the Rh-positive child is born.

In the event of jaundice, then phototherapy, that is, exposing the baby to specialised light, is used to help speed up the removal of bilirubin. In severe cases, if phototherapy isn’t working, blood transfusion may also be administered pre and post birth. The child may also be given intravenous immunoglobulin to help expel the bilirubin faster.

If a mother has already been sensitised (this can be determined through a special blood screening test), then they are considered to have high risk pregnancies and from that point on, are under close monitor by medics.

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