Question

how did the discovery of the rhesus factor affect society?
more patients died from having a transfusion with the wrong rhesus factor.
new treatments during pregnancy could prevent harm to the developing child.
less donated blood could be used in the treatment of patients.
the number of blood types was reduced by half.

Explanation:

The discovery of the rhesus factor led to new medical understandings. In pregnancy, if a mother is Rh - negative and the fetus is Rh - positive, the mother's immune system can attack the fetus. However, with the discovery of the rhesus factor, new treatments (like Rh immunoglobulin) during pregnancy could prevent harm to the developing child. Option 1 is incorrect as proper knowledge of rhesus factor reduces transfusion - related deaths. Option 3 is wrong because more blood can be properly utilized with rhesus factor knowledge. Option 4 is incorrect as the number of blood types (considering Rh factor) actually increased the complexity of blood typing rather than reducing it.

Answer:

New treatments during pregnancy could prevent harm to the developing child.