Define Erythroblastosis Fetalis

Besides the risk of a mismatch reaction during a second or during any subsequent  blood transfusion, giving Rh-positive, blood involves  risk in case of young Rh-negative girls.

This  is because of the  possibility of complication during  pregnancy if the  girl happens  to have  a Rh-positive foetus  in  her uterus any time later  in  life. The chances of any abnormalities resulting from Rh incompatibility are negligible during first pregnancy, 3% during second and 10% during third. This is due to following reasons:

1)  Red cells of the foetus are unable to cross normal placenta. There has to be some abnormality  in the placenta  before foetal red cells can enter the maternal circulation.

2)  Foetal red cells may be destroyed by maternal plasma before they can induce an antibody response. E.g., if mother is 0,  Rh negative  and the foetus  is A, Rh positive, the foetal red cells would be haemolysed by  the anti-A antibodies present in the maternal plasma.

3)  If the foetus and mother happen to be of same group, i.e., A,B or AB but mother is Rh -ve  and foetus Rh +ve,  during 2nd  and subsequent  pregnancies, mother gets sensitize with Rh antigents of  fetal blood,  resulting  in production  of anti-Rh  antibodies, which will destroy  foetal RBC, causing 'erythoblastosis foetalis'.

Although erythroblastosis foetalis may be  treated by exchange transfusion, the prevention is  routinely attempted  by desensitizing the mother for production of Rh antibodies during pregnancy. The desensitized mothers don't respond  to  foetal Rh+ve RBCs. Thus erythroblastosis foetalis is prevented.

Apart from the Rh incompatibility as a complication leading to loss of blood, there is another condition wherein the RBCs are deficient. This is referred to as anaemia, a disorder related to deficiency of erythrocytes. As a student of dietetics, you must be familiar with anaemia and its consequences.