The sterilisation operation was found to have been performed correctly, but a fistula had formed after the operation that enabled pregnancy to occur. File photo.

A newborn baby dying after a delayed diagnosis of pneumonia, missed tumours and the accidental amputation of body parts were among almost 550 serious medical errors in New Zealand's hospitals in the past year.

Other patients endured the heartbreak of stillbirth, were left blind after delays in care and suffered broken limbs after needless falls.

Some 542 adverse events - unintended or unexpected events that result in a patient being harmed - were recorded in district health boards (DHB) across the country in 2016-17, up slightly on the 520 the previous year.

CHRISTEL YARDLEY/STUFF Patients endured stillbirth, had cancerous tumours missed and suffered broken limbs after needless falls.

Of those, 79 people died, although not necessarily because of the mistakes.

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* Adverse event reports from the South Canterbury District Health Board double

* More than 500 New Zealand patients suffered after health failures in the past year

But Health Quality and Safety Commission (HQSC) chairman Professor Alan Merry said he believes hospital care in New Zealand is as safe as anywhere in the world.

He said: "The vast majority of care goes well, people are successfully treated and these events are a small proportion of the overall picture.

"We do have an excellent system and it's largely safe, and these incidents are the exception.

"It doesn't diminish their importance and the fact that we report them is a good thing. But we don't want to see them and take them very seriously."

He also said there had been a "steady improvement ... towards increased transparency and taking action based on learnings from system failings".

Around three million people are treated in the country's public hospitals each year, with around one visit in every 5,535 resulting in an adverse event.

A further 86 adverse events were recorded in private surgical hospitals, ambulance services, residential care, primary health organisations and hospice and community services; events relating to mental health care are reported separately.

Twenty DHBs outlined individuals cases to the HQSC, with varying degrees of detail.

Among them were:

* Nine patients between the ages of 50 and 93 suffering harmful falls, including a bleed to the brain, a dislocation and fractured limbs. (Northland)

* A delay following treatment for haemorrhoids leading to the late discovery of a rectal tumour, and a patient going blind after a delayed follow-up for treatment of macular degeneration. (Northland)

* The wrong patient being anaesthetised for a procedure, two patients having allergic reactions after eating meals containing allergens, and a person having a cardiac arrest after the wrong settings were made on a pacemaker. (Auckland)

* A patient who should have been given blood thinning medication died from a blood clot on the lung after surgery, another had the wrong skin lesion removed, and medical staff had to retrieve part of a dental plate stuck in a patient's throat following general anaesthetic. (Waitemata)

* A patient was left blind after being given the wrong amount of drugs, a one-month-old baby suffered liver damage after receiving a massive overdose of paracetamol and a patient's nose was burned after an acid was accidentally applied. (Counties Manukau)

Canterbury DHB had 73 adverse events identified as serious, a marked rise on the 43 last year, with 29 patients suffering falls while in hospital - accounting for the largest proportion of its major medical errors.

The DHB gave little details of individual events but said 20 patients also developed unnecessary pressure injuries while in hospital, the first time such injuries have been reported among its serious events.

Of the 542 adverse events recorded across the country, most were seen in Auckland, followed by Canterbury and Southern DHBs - though comparisons are difficult because of varying populations.

The majority related to clinical management events, the HQSC said, while serious failings also led to a large number of falls, pressure injuries and healthcare associated infections.

Prof Merry said the rise in pressure injuries could reflect efforts to raise awareness of their impact and devastating harm, saying: "This attention is particularly important given evidence shows pressure injuries are highly preventable."

Jane MacGeorge, from the New Zealand Nurses Organisation, said more needed to be done around "concerning" levels of pressure injuries, infections in hospital and failures to save deteriorating patients.

She said: "These particular indicators need to be monitored specifically, not as part of a homogenous group as they are a barometer of quality of care and typically observed in an under resourced system."

And she blamed underfunding of the health service for low staff levels, saying: "With a new government promising reinvestment we expect the situation for patients and health staff to improve."