Rhesus

In Greek mythology, King Rhesus of Thrace fought for Troy during the Trojan War. His famous horses were stolen by Diomedes and Odysseus.

Iliad X, 435

Rhesus (Rh) is a blood group (name taken from the Rhesus Monkey). Humans have either Rh positive or Rh negative factor associated with their red blood cells (RBC's).

Matching Rhesus factor blood types as the ABO system is very important and mismatching (i.e. an Rh positive donor to an Rh negative recipient) will cause hemolysis.

The second born Rh positive child of an Rh negative mother will also have hematological problems mainly hemolysis. Hemolysis is the process of red blood cell rupture, in this case, being attacked by antibodies directed at the RBC's.