Mal Cadwallader is still waiting for answers over the death of her mother, and that of the brother she never met.

Her mother, Kelle Cadwallader, of Invercargill, was 34 weeks pregnant when she died on September 17, 2014.

Two days earlier, the 37-year-old was taken to Southland Hospital complaining of chest pains, but was sent home after being told she had acute indigestion.

Supplied Kelle Cadwallader was 34 weeks' pregnant when she died on September 17, 2014.

The following day, she suffered a suspected heart attack, later pleading with medical staff to save her baby, whom she had named Archer.

Cadwallader, who was never told her baby had died, later died in Dunedin Hospital following bypass surgery.

Asked for an update into the investigation into her death, Southern DHB chief medical officer, Dr Nigel Millar, said the health board always "strive to deliver safe care to our patients and thoroughly investigate incidents which sadly do occur".

"This was a tragic death and our sympathies are with the family of Ms Cadwallader."

Her death had been "fully investigated" with an internal and external review conducted, including an investigation by the Perinatal and Maternal Mortality Review Committee.

That investigation remains confidential.

That was little comfort for Mal Cadwallader, who has heard nothing from health officials.

"They really kind of made it an open and shut case. They said it was a tragic accident and nothing else became of it.

"I've heard three different stories on how mum actually died, and I'm really not sure what one to believe because they all seem so surreal.

"All I know is that the doctors sent her home thinking it was indigestion when mum was adamant that something was seriously wrong."

Cadwallader said her mother had heart issues and knew the symptoms to watch out for "but it was all overlooked".

She believed a nurse or doctor who was experienced with pregnant patients would have picked up the warning signs.

Cadwallader was also unaware of a 2015 coroner's report until it was supplied by Stuff.

That report noted that her mother, who weighed 130kgs and had a history of asthma and pre-term delivery, died of aortic dissection, a rare incident affecting four patients for every 100,000 people.

The coroner, David Crerar, noted in his findings that the risk factors associated with Kelle Cadwallader could have been considered in greater depth by the team in charge of her care.

"I am confident the Southern District Health Board and its clinicians have learned from the circumstances of the death of Kelle Cadwallader and that such circumstances (acknowledged to be extremely rare) are unlikely to recur."

A spokesman for the Perinatal and Maternal Mortality Review Committee said cases where a mother and baby have both passed away in hospital were highly unusual and required considerable investigation.

The committee reviewed perinatal and maternal death, in order to reduce deaths and improve the quality of care provided nationally, he said.

Legislation meant the committee was prohibited from releasing any information about individual or identifiable cases, including the status of reviews.

"Investigations to identify why specific patients died and communication of their findings to family members is the responsibility of the relevant district health board, and the Coroner," he said.

Cadwallader said the death of her mum and brother had devastated the family.

"Not even my family will talk about her death now. It's like she never existed."

"I think that not knowing is the worst thing to happen. It hurts a lot. But sadly this is life."

To help cope with their loss, Cadwallader and her two brothers would carry on their tradition of spreading their mum's ashes on the anniversary of her death.