Hemolytic disease of the newborn, is a very common clinical condition seen in the second child born to Rh negative mother.For this disease to occur, the mother should be Rh negative and the child must be Rh positive.Here the chance for the child to be Rh positive increases when the father is Rh positive.In this case the problem occurs only with the second child and the first baby usually escapes.So what happens in Rh incompatibility?.Why the first child escapes from this disease and only the second child is effected?.What are the treatments given for the Rh negative mother?.These questions are answered by this article in a very simplified and detailed manner.
Before explaining about the disease, lets have a brief idea about Rh factor.Rh stands for Rhesus which is derived from the name of Rhesus monkey in which the factor was discovered for the first time.When a person is said to be Rh positive, it means that a Rh protein is present in the cell membrane of Red Blood Cells or RBC.If the Rh protein is absent, such people are said to be Rh negative.Now lets take a case of blood transfusion.Suppose you give a Rh positive blood to a Rh negative person, the recipient here who is Rh negative will start to produce antibody against Rh protein in the donors blood.The reaction between the Rh positive (antigen) and anti-Rh antibody is called agglutination.As a result a clot like substance will be formed, which will effect the blood flow.Also due to the breakdown of RBC and hemoglobin, a substance called bilirubin will be formed.This bilirubin is responsible for the yellow colour in jaundice.Here the bilirubin formation will prove fatal to children below the age of 1 year.Now we can see about the Rh incompatibility in case of Rh negative mother and Rh positive child.
What is Rh incompatibility?
Suppose the mother is Rh negative and father is Rh positive.There is more chance that the child born to them are Rh positive.Lets consider the case of their first child, and let the blood group of that child be Rh positive itself.Consider the child is still in the womb.In the uterus the connection between fetus (child in womb) and mother is through placenta and exchange of materials take place through it.This placenta ensures that there is no mixing of blood of mother and fetus and the substance in blood diffuses in both direction through placenta.Since there is no mixing of blood, the Rh positive blood of fetus wont enter the mother's body and no antibody against Rh protein will be produced in mother's body and no harm is done to the child.But during child birth (parturition), the placenta breaks and there will be mixing of some blood of the child with the mother's blood.When this happen, the mother's blood which is Rh negative will start to produce anti-Rh antibody against the Rh positive blood of fetus and there will be little agglutination reaction.But no harm is done to both mother and child, because the child is already out of mothers body and in case of mother only a little amount of blood has entered and there wont be any big effect.But the problem here is that, the antibody produced in the mother's body will remain there and it will always be present in the blood.This antibody has the ability to cross placenta.Now lets take the case of the second child born to them.Suppose the second child is also Rh positive.Here we have to remember that anti-Rh antibody are still in mother's blood.So once the placenta is formed and exchange of materials take place between mother and fetus, this anti-Rh antibody which has the ability to cross placenta will also cross the placenta and reach the fetus.Thus agglutination reaction will start in the fetus blood and fetus RBC be attacked and destroyed in large amounts.This condition is called Rh incompatibility.
Consequences of Rh incompatibility
In Rh incompatibility, the RBC of the fetus is getting attacked by the antibody from mothers blood.As a result destruction of RBC take place which is called as hemolysis.Thus the name of the disease is Hemolytic Diseases of the newborn.Sometimes the child is born with severe hemolytic disease and then it is referred to as Erythroblastosis fetalis.As i have mentioned earlier, there is one more problem caused by destruction of RBC, which is the formation of a substance called bilirubin.In young children before the age of 1 year, the part of brain called Blood Brain Barrier will not be fully matured.As the name implies, it is a barrier and it act as filter for substance entering the brain.So the substance from blood will start to get deposited in brain.When this free bilirubin gets deposited in brain it will lead to serious condition called Kernicterus.This will lead to mental retardation, fits and other sever conditions.
Prevention is the best medicine.If the mother is Rh negative and child is Rh positive in the first delivery, an injection will be given to the mother to destroy the anti-Rh antibody formed in the mother's blood.One of the commercially available shot is called Rhogam.Now suppose if this precaution was not taken and a second child is born to them with hemolytic disease or erythroblastosis fetalis, then immediate action must be taken which include exchange transfusion(giving fresh blood), photo-therapy, and treatment with medicines like barbiturates.The concept behind photo-therapy is that, when child is kept under a blue light of 440nm wavelength, the bilirubin present in the body which is not much soluble, will isomerize to a more soluble form and thus it will be easily excreted through urine.
This is the case of Rh incompatibility leading to hemolytic disease of new born and erythroblastosis fetalis.So next time when a Rh negative mother delivers a Rh positive child, necessary treatment must be given as soon as possible.Thus any severe condition of Rh incompatibility can be prevented in the future.