**Core Concept**
Haemolytic disease of the newborn (HDN) is a condition where the red blood cells of a fetus or newborn are destroyed faster than they can be made. This occurs due to the incompatibility between the blood types of the mother and the fetus.

**Why the Correct Answer is Right**
Haemolytic disease of the newborn is a classic example of an autoimmune reaction, where the mother's immune system produces antibodies against the RhD antigen present on the fetus's red blood cells. These antibodies can cross the placenta and bind to the RhD antigen on the fetus's red blood cells, marking them for destruction. This leads to the breakdown of the fetus's red blood cells, resulting in anaemia and potentially life-threatening complications.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Haemolytic disease of the newborn is not an example of a genetic disorder. While genetic factors may contribute to the condition, it is primarily an autoimmune reaction.

**Option B:** This option is incorrect because Haemolytic disease of the newborn is not a result of a bacterial infection. While infections can trigger autoimmune reactions, HDN is caused by an incompatibility between the blood types of the mother and the fetus.

**Option C:** This option is incorrect because Haemolytic disease of the newborn is not an example of a congenital anomaly. While congenital anomalies can affect the fetus's red blood cells, HDN is a result of an autoimmune reaction.

**Clinical Pearl / High-Yield Fact**
To prevent Haemolytic disease of the newborn, RhD-negative mothers are often given RhD immunoglobulin (RhIg) during pregnancy and after delivery to prevent the formation of antibodies against the RhD antigen.

**Correct Answer:** D.