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.

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

Explanation:

The rhesus factor is an antigen present in the blood of humans and other primates, this is very important because the RH factors are uncompatible between them causing that for example is someone is RH positive and receives a tranfussion of RH negative it can cause its blood to coagulate in minutes, leading to death, so the discovery of the RH factor allowed to have safer trnasfussions of blood, and to help pregnant woman that had different RH factors than her babies to be treated in order to not harm the baby with their blood.