Rh Disease (also known as rhesus Isoimmunization, Rh (D) Disease, or Rhesus Incompatibility, and Blue Baby Disease) is a type of Haemolytic disease of the Foetus and Newborn (HDFN). HDFN due to Anti-D Antibodies is the proper and currently used name for this disease as the Rh Blood Group System actually has more than 50 Antigens and not only the D-antigen. 
The term Rh Disease is commonly used to refer to HDFN due to Anti-D Antibodies, and prior to the discovery of Anti-Rho(D) Immune Globulin, it was the most common type of HDFN. The disease ranges from mild to severe, and occurs in the second or subsequent pregnancies of Rh-D Negative women when the biologic father is Rh-D Positive.