The problem is the absence of that Rh (e.g. O-) in a
woman who is married to a man that has Rh (e.g. O+). This can result in the
death of their unborn baby. The disease is called Haemolytic disease of the
Newborn. The process that leads to the disease is called Rh iso-immunization.
Let us see how this occurs.
A baby inherits its blood group from its parents. The
inheritance pattern for the Rh is shown in the picture below.
If the baby inherits the Rh+ve blood group, and the
mother is Rh+ve, there is no problem as far as this disease is concerned. However, if
the mother is Rh-ve, then there is a problem.
Let me explain what antigens and antibodies are because
we will be using these terms often. Antigens are on every living thing. They
are like ID cards. Apart from identical twins, no two persons have exactly the
same antigens. Antigens are just things that your immune system identifies to
confirm ownership. This means if your immune system comes in contact with
anything, it will kind of scan through it to check if the antigens on the
foreign body corresponds to the antigens in your own body. If there is even a
slight mismatch, the immune system destroys that thing using antibodies.
Allow me introduce the term sensitization. This means that a
woman without the Rh antigen has little or no antibodies against any blood
containing the Rh antigen. This is because our body produces antibodies against
foreign bodies only when we are exposed to those agents, this is what we try to
achieve with immunization. There are some antibodies that are naturally present
in our body; these do not require sensitization e.g. ABO blood group antibodies.
The sensitization of an Rh-ve woman is what we do not
want; should this occur, all subsequent Rh+ve pregnancies would either be
terminated or the babies would be born with severe anaemia, leading to a
condition called kernicterus which causes brain damage to these babies.
The first Rh+ve pregnancy (not the first delivery) is
usually spared because the body needs time to produce antibodies.
How can a woman be sensitized?
First, her blood group must lack the Rh, which means
Rh-ve (A-, B-, AB- or O-). Then she must come in contact with Rh+ve blood. This
occurs through several ways:
· Miscarriage or during induced abortion, where
they baby was Rh+ve, having inherited it from the father. Most Rh-ve women come
to the hospital with what they call their ‘first’ pregnancy, forgetting the
abortions and miscarriages they might have had in the past. The blood of the baby usually enters
the mother’s circulation to cause sensitization.
·
Bleeding during pregnancy (called ante partum
haemorrhage).
·
Blood transfusion with Rh+ve blood.
·
Medical test on the baby while still in the
womb.
What can be done?
After sensitization, nothing can be done. Therefore the
aim is to prevent sensitization of the mother. This is done by giving the woman
a drug called Rhogam, to clear the foreign antigens in the blood before the
immune system sees them.
In most developing countries, facilities for testing the
blood group of the baby while in the womb either does not exist or the test is
very expensive. However, in a country that has the facilities, Rh-ve women at
risk, have the blood group of their babies determined before taking Rhogam.
This is due to the fact that the baby starts expressing Rh antigens at about 30
days of age.
KNOW YOUR BLOOD GROUP AND THAT OF YOUR PARTNER
TODAY!!!!!!!!!!!!!
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