There's been a four percent increase in the number of medical mishaps in New Zealand hospitals.

The Health Quality & Safety Commission's annual Safety in Hospitals report shows there were 454 serious adverse events in the past year, including 73 in which the patient died.

Broken bones from falling over in hospitals was the most common cause of harm reported by DHB's.

There were 11 cases where something was left inside a patient during a procedure, such as needles, surgical equipment or swabs.