Termination of resuscitation requires online medical control approval when the patient is in which of the following situations?

When evaluating the termination of resuscitation efforts, the presence of a Do Not Resuscitate (DNR) order is a crucial factor that necessitates online medical control approval. A DNR indicates that the patient has made a formal request, often in the context of a terminal condition, to refrain from aggressive resuscitation measures. This empowers paramedics to respect the patient's wishes and follow protocol accordingly.

In the context of the other options, while age, pregnancy status, or the presence of massive trauma can influence medical decisions in emergencies, they do not specifically trigger a requirement for medical control approval to terminate resuscitation. Only a DNR order directly signifies that resuscitation should not be pursued, barring further medical directives. Therefore, the presence of a DNR is the key determining factor that necessitates obtaining online medical control's approval before proceeding with terminating resuscitation efforts.