Neonatal haemolysis, also known as neonatal haemolytic disease, is a homozygous immune haemolytic disease caused by a blood group discrepancy between mother and baby.
Normally, the blood type of the foetus is determined by both parents, but the child with the disease inherits blood group antigens from the father that his mother lacks.
When the foetal red blood cells pass through the placenta to the mother, these paternally inherited blood group antigens stimulate the mother to produce the corresponding antibodies; these antibodies enter the foetal circulation through the placenta and bind to the corresponding antigens on the surface of the foetal red blood cells, which are destroyed in the monocyte-phagocyte system, causing haemolysis, which manifests as anaemia, oedema, hepatosplenomegaly and a short period of time after birth progressive severe jaundice.