I recall my first day of posting in the Neonatal ward, I saw a child whose eyes were shut close and kept under the UV light for what was called UV therapy and my curiosity skyrocketed. The question "why" kept popping into my head and I watched the miracle of turning a once yellow pale skin colored baby to bright pink.
The baby was diagnosed with Hemolytic disease of the newborn and the first step of therapy was UV or phototherapy. So, how does a baby get born with such dreaded diseases? It's quite simple, Rhesus incompatibility.
In my previous post, I explained the ABO blood grouping and I also introduced the Rhesus factor. The Rhesus blood grouping system has its major Importance in maternity sciences. Rhesus factor was named after the money Rhesus when it was discovered that a significant human blood population reacted to the serum of the monkey.
A Person can either be
1) Rhesus Positive, and hence, his red blood cells contain the Rhesus antigen.
2) Rhesus Negative, and hence, his red blood cells do not contain the Rhesus antigen.
Like I previously said, the two most important blood grouping systems amongst many are the ABO grouping and the Rhesus system. Most humans know their ABO and Rhesus blood group, hence you may hear something like O+, meaning the person is an "O" ABO grouping and positive for Rhesus antigen.
Rhesus factor as I earlier described gets it's a core application in medicine via maternity and childbearing science. It's always important to educate women who are Rhesus Negative on the implications of their blood group when it comes to maternity and childbearing.
To understand why it is important, we need to deviate a little and talk about antigen-antibody Reactions. It's quite simple, an antigen would react to its corresponding antibody to produce a Reaction. In the human blood, this Reaction leads to agglutination or coagulation of blood cells, hence, transfusion Reaction.
So how does this affect pregnancy and childbearing?
This Rhesus system is only applicable to childbearing when
1) The mother is Rhesus Negative
2) The father of the child is Rhesus positive
When the woman becomes pregnant, following Mendelian law of inheritance, the child may likely be Rhesus positive or Rhesus Negative, as the child may inherit either the mother's or the father's Rhesus group. If the child is Rhesus Negative then there would be no problem, but if the child is Rhesus positive, then this is where the problem arises.
During the entire pregnancy stage, the child's blood is prevented from mixing with that of the mother via the placenta, but during Parturition, the placenta may be damaged and the baby's blood may mix with that of the mother.
Now recall that the mother is a Rhesus negative and hence has no Rhesus antigen, and unlike ABO blood grouping systems in which the antibodies of the antigens are naturally occurring, that if Rhesus isn't, hence a person cannot develop the Rhesus antibody without being exposed to the Rhesus antigen.
In context, the first pregnancy of a Rhesus Negative mother and Rhesus positive father is usually safe. After the first delivery and the woman's blood gets mixed with the baby's, she gets sensitized by exposure to the Rhesus antigen and hence, she would develop the Rhesus antibody.
If the mother gets pregnant again, and the baby is a Rhesus-positive baby, then the already developed antibodies in the woman's blood could easily pass through the placenta barrier into the baby's blood, and you know what happens when an antigen meets an antibody? Reaction!
So basically, the antibodies produced by the mother because of the first pregnancy could pass through the placenta barrier and begin to react and in a sense attack the baby's antigens on the red blood cells, hence also attacking the red blood cells.
Now, we can explain what Hemolytic disease of the newborn is
Hemolytic disease of the newborn, HDN is a disorder in which the red blood cells of the baby which is supposed to last for 120 days are quickly destroyed because of in vitro sensitization of the red blood cells by the mother's antibodies, Rhesus antibodies, as it can only occur in the case of a Rhesus Negative mother who has the Rhesus antibodies and a Rhesus positive baby.
The systems include Edema (swelling), Jaundice, shortness of breath, and so on. The baby is born pale and yellow and if treated late, may lead to multiple organ failure and so on.
How does this happen?
The mother's antibodies get attached to the baby's red blood cells and this gives signals to the baby's reticuloendothelial system to begin to destroy any red blood cell that has been sensitized by the mother's antibodies, thus killing them prematurely. Another Important symptom is low PCV it packed cell volume.
Jaundice comes about due to the high rate of red blood cell destruction and its conversion to bilirubin which is not quickly removed from the body.
Treatment and prevention
To prevent the mother from being sensitive by her first pregnancy, Rhogam, which is an artificial antibody to the Rhesus antigen uses the competitive antigen-antibody principle to bind to any Rhesus antigen from the baby's blood that may have entered the mother's circulation and destroy them by reacting with them and neutralizing them, hence they wouldn't be able to sense the mother to produce the Rhesus antibodies.
Rhogam is effective when given to the mother within 72 hours of delivery.
Treatment for the baby includes
1) Fresh blood transfusion to cope with the Low PCV
2) UV or Phototherapy for Jaundice. UV light is believed to be able to break down bilirubin to its constituent molecules and hence, be easily removed from the body.
Thanks for reading.
