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 knowledge about blood - related conditions in pregnancy. In cases where a mother is Rh - negative and the fetus is Rh - positive, antibodies can be developed that may harm the fetus. With the discovery of the rhesus factor, new treatments like Rho(D) immune globulin during pregnancy can prevent the mother's immune system from attacking the developing child.

Answer:

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