"Sexual activity is mechanically dangerous, potentially infectious and stressful for the cardiovascular system."
According to this retrospective review of 11 years of electronic health records from University Hospital Bern, Switzerland, they identified 445 patients seeking emergency care secondary to sexual intercourse. The majority of emergency department visits were secondary to suspected infectious etiologies (62%), but neurologic complaints, trauma, and cardiovascular incidents comprised the remaining portion.
The trauma portion probably speaks for itself without need for additional detail. There was one myocardial infarction and one aortic dissection. Among the "various complaints", two patients were diagnosed with "eczema". However, among the neurologic emergencies, there were 12 cases of subarachnoid hemorrhage and 11 cases of – ah – "transient global amnesia".
All things being equal, at least, sexual activity was only associated with 0.1% of emergency department visits – hardly the most dangerous of potential choices of recreation.
"Sexual activity-related emergency department
admissions: eleven years of experience at a Swiss university hospital"