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.

The discovery of the rhesus factor had a significant impact on society, particularly in the fields of medicine and transfusion practices. Here's how it affected society based on the options provided: 1. **More patients died from having a transfusion with the wrong rhesus factor.** - This statement is somewhat misleading. The discovery of the rhesus factor actually aimed to reduce the number of transfusion reactions and deaths by identifying the compatibility of blood types. However, before this discovery, many patients did suffer from complications due to incompatible blood transfusions. 2. **New treatments during pregnancy could prevent harm to the developing child.** - This is a true and significant impact. The discovery of the rhesus factor led to the understanding of Rh incompatibility in pregnancy, where an Rh-negative mother could produce antibodies against the Rh-positive blood of her fetus. This can lead to hemolytic disease of the newborn (HDN). With the introduction of treatments such as Rh immunoglobulin (RhoGAM), many cases of HDN can now be prevented, significantly improving maternal and child health. 3. **Less donated blood could be used in the treatment of patients.** - This statement is not accurate. The discovery of the rhesus factor actually allowed for better matching of blood types, which means that more donated blood could be effectively used in transfusions, rather than being discarded due to incompatibility. 4. **The number of blood types was reduced by half.** - This statement is incorrect. The discovery of the rhesus factor did not reduce the number of blood types; rather, it added complexity to the existing ABO blood group system by introducing the Rh factor, which is an additional classification. In summary, the most accurate statement regarding the societal impact of the discovery of the rhesus factor is that **new treatments during pregnancy could prevent harm to the developing child.** This has had a profound effect on maternal-fetal medicine and has saved countless lives.