D. Hildbrand

The Rhesus Factor

When we want to give blood to another person we have to make sure the bloods are compatible and will not agglutinate. It is not only the ABO antigens that need to be matched, there are a large number of other antigens which go under names like M, N, S, and Lewis factors.

The rhesus factor (Rh-factor) is so named because the antigen was first discovered in rhesus monkey blood. Individuals whose red blood cells contain this antigen to rhesus monkey blood are called rhesus positive (Rh+). Those whose blood does not agglutinate rhesus monkey blood are called rhesus negative (Rh-). The Rh antigen is found on the red blood cells of 85% of whites, 92% of blacks and most Orientals.

Rh + Rh -

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Whites 85% 15%

Blacks 92% 8%

When we match up bloods for transfusion we must consider the Rh factor as well as the ABO group because an Rh- individual cannot receive Rh+ blood. He becomes sensitized and will produce anti-Rh antibodies on the first transfusion. On any following transfusion of Rh+ blood agglutination will occur.

If a Rh- mother becomes pregnant by a Rh+ father, the baby may inherit the Rh factor. This means a Rh+ baby growing in a Rh- mother. Before birth and during the birth process some of the baby's blood gets into the mother's circulation. This sensitizes the mother to Rh+ blood and she produces anti-Rh+ antibodies. These antibodies do not affect the first baby as they are produced in her blood after this baby is born. If she has a second pregnancy with a Rh- baby, however, her antibodies may cross the placenta and destroy the baby's red blood cells. This condition is called erythroblastosis foetalis. The baby either suffers from jaundice , dropsy and anaemia or quite often it is stillborn. If these symptoms are not treated immediately his nervous system will be damaged resulting in feeble-mindedness and other serious brain damages. These serious damages can only be prevented by a complete exchange of the newly born baby's blood.

How can such serious damage be prevented right from the beginning?

About 15 years ago preventive treatment was introduced. The mother is given an injection containing RH+ antiserum after the delivery of her first child. These antibodies attach to RH+ blood cells and neutralize them, thus preventing the production of anti-RH+ antibodies. In order to make sure that this injection protects the second child from erythroblastosis foetalis the following precautions have to be taken:

1. The RH- blood of the mother must not contain any anti-RH+ antibodies yet. So women should have their blood tested during the first pregnancy to find out whether they belong to the small group of people with rhesus- blood.

2. The RH+ antiserum must be given within 72 hours of the delivery of the first child.

to be compatible - vereinbar sein, zusammenpassen ( = to be matched); to agglutinate - to clump together; to become sensitized - empfindlich oder sensibilisiert werden; to occur - to happen; to inherit - erben, übertragen bekommen; to affect - beeinträchtigen, schädigen; jaundice - Gelbsucht; dropsy - Wassersucht; anaemia - Blutarmut; stillborn - totgeboren; feeble-mindedness - Geistesschwäche; to prevent - to stop; precautions - Vorsichtsmaßnahmen; delivery - here: birth

Questions

Go though the text and find out the answers to the following questions.

1. When is the rhesus factor really dangerous for babies?

2. What happens during the first and second pregnancy?