Erythroblastosis Foetalis
• This occurs:
– If the fetus is Rh positive and
– mother is Rh negative
• Some fetal red cells cross the placenta and enter maternal circulation in all pregnancies
– The Rh +ve fetal cells act as foreign antigen and stimulate production of Rh antibodies in the Rh negative mother
• The Rh antibodies are of two main types:
– The ‘strong’ or saline antibodies and
– The ‘weak’ or albumin antibodies: these are small 7s gamma globulins which can cross the placental barrier.