The color of human blood all over the world irrespective of the colour of the skin, race,political belief, religion is red. Because of the presence or absence of some chemical compounds in the red cell membrane of the blood, it is accepted that there are 29 types of major and minor blood groups. However, for transfusion purpose, only ABO and RH groups are considered.

The Rhesus Blood Group

One blood group besides the ABO group is of utmost importance in transfusion - the Rhesus (Rh) Group. This substance is carried, like the A and B substances, on the membrane of the red cells of the blood. The Rh substance is so called because in certain aspects, it resembles a substance occurring in the red cells of the Rhesus monkeys. Dr. Karl Land Steiner who received the Nobel Prize in Medicine in 1930 for his discovery of ABO groups, discovered Rh factor of blood in USA in 1940 along with a young research worker Dr. Alexander Weiner About six out of every seven people in white population have in their blood, Rhesus substance. But dark races including Indians are almost always 97% Rh+. Those who have the Rh factor in their red corpuscles are called Rhesus positive (Rh+) and those who lack the factor are called Rhesus negative (Rh-). There is virtually no ‘naturally occurring’ anti Rh antibody; but if Rh positive blood is transfused to Rh negative patient, it is likely that he/she would form an anti Rh antibody which might be strong or weak. occurring’ anti Rh antibody; but if Rh positive blood is transfused to Rh negative patient, it is likely that he/she would form an anti Rh antibody which might be strong or weak.

Blood groups are inherited from parents, according to a certain Mandelian theory. Blood group can never change in lifetime. Rhesus Babies (Haemolytic Disease of Newborn) If the father is Rh positive and the mother is Rh negative, the child can be Rh negative like the mother or Rh positive like the father. If the child is Rh negative like the mother, there would not be any problem. If the child is positive like the father then there can be problem, if not in the first pregnancy but in subsequent pregnancies unless taken care of after the first delivery. One in 1200 of children in India is born as a 'Rhesus Baby'. Before delivery, blood may leak from the child in the womb into the circulation of the mother. Mother's defence mechanism is alerted with the entry of this 'foreign body'. She starts producing anti Rh positive red cells.

The anti bodies remain in her blood for a few months after the delivery and may then disappear. But she is now permanently sensitised and if Rh positive cells enter into her circulation again at the time of the subsequent pregnancy, she will respond after 72 hours by making anti Rh positive antibodies on a large scale, which passes into the baby in the womb and attack its red cells. Red cells of the baby are destroyed and release a pigment yellow in colour. The baby may die in the womb or is born with Haemolytic Disease of the Newborn (HDN)Saving Such BabiesBefore 1960, technology of saving the life of such babies was not known. To save the life of such babies transfusion is needed. Exchange transfusion is the gradual removal of the baby's blood and its replacement by Rh negatine or mother's group specific negative blood.

This blood for such transfusion should not be more than five days old. Nowadays, anti Rh positive anti body (a protein called immunoglobulin present in the plasma of the people sensitised to Rh factor) is refined and concentrated and injected to Rh negative mother within 60 hours of her giving birth to a Rh positive first issue. It has the effect of causing any Rh positive cells, which have passed from the baby's to the mother's circulation to be neutralized in her blood. Rh negative mothers treated in this way do not become sensitised unless a large a number of red cells have passed from the child to the mother. However, once a mother has become sensitised and form Rh antibodies, there is no method of removing them. This injection is administered only to Rh negative mothers who are not already sensitised mothers since the leakage of blood from the child in the womb to the mother takes place at the last stage of the pregnancy.Often the child is taken out a few weeks before the full term by caesarian section to prevent complication.

What Should Be Done

It is prudent to advice the family to organise one or two ‘O’ negative (O-) or mother's group specific negative donor well in advance before the scheduled date of delivery.

If the situation warrants, these donors may be called upon to donate blood for exchange transfusion to the newborn, if appropriate blood is not available in the blood bank. A timely action in such a case makes the difference between life and death.

Isha Majumder

BA (Journo, Psy & Eng)