Kerri-Ann drove home and left her two toddlers in the back seat of the car. Hours later, she woke up and found horrific scenes. Now authorities want to know: could anything have saved Darcey-Helen and Chloe-Ann?

Decisions made by Queensland's Child Safety Services will be put under the microscope as part of a coronial inquest into the deaths of two sisters who were left inside their mother's car for hours in soaring temperatures.

Darcey-Helen, two, and Chloe-Ann, 18 months, died after their mother, Kerri-Ann Conley, left them inside her car for more than nine hours in direct sunlight.

Conley had arrived back at her home in the southern Brisbane suburb of Waterford West after 4am on November 23, 2019.

She left her children in their carseats in the back of the car before going inside her home and falling asleep.

When she woke, she went outside to the car about 1pm and found both daughters unresponsive.

Ambulance officers arrived a short time later but both girls were declared dead at the scene.

They had each died of hyperthermia, after being left in the car, which had reached more than 50C at the height of the day.

Conley was sentenced to nine years in jail in February this year after pleading guilty to manslaughter.

Coroner Terry Ryan will now examine whether there were any failings or missteps taken in the lead up to the girls' deaths.

Counsel assisting the coroner, Simon Hamlyn-Harris, said during a pre-inquest hearing on Monday in Brisbane the inquest would look to examine the appropriateness of the responses of Child Services, Logan Hospital and Queensland Police Service before the girls deaths.

It will also examine how the departments' knowledge of Conley's drug use had impacts on the children.

Mr Hamlyn-Harris said Conley was a heavy user of methamphetamine and was known to pass out while using drugs.

'Her behaviour as a result of her drug lifestyle clearly put the girls at a significant risk of harm,' he said.

'There's evidence she regularly left them in the car if they were asleep when they got home.'

'She had a habit of leaving the children with whoever was at the house, saying she would get cigarettes but wouldn't return for a long periods of time.'

Mr Hamlyn-Harris said Child Safety was first alerted to Conley after the birth of her first child, Darcey-Helen, in May 2017.

He said hospital staff where Darcey-Helen was born had raised concern about Conley's lack of attachment with her child after giving birth, and how she seemed to leave the maternity ward without any concern for her baby's needs.

The court was told the hospital was not aware of Conley's drug use.

Child Services were involved in Darcey-Helen's care from her birth to July 2018, when United Care took over the care plan.

The court was told Conley disengaged with the service and care stopped on February 11, 2019.

Mr Hamlyn-Harris said Child Services had received an anonymous 'notification' when Darcey-Helen was about four months old that Conley was a 'daily ice user, driving all night long with baby in the car' and had 'smashed up three cars since the baby as born because she'd nodded off'.

'She was asking for money for milk or formula and (would) stay awake for days then have a few hours of sleep then go off looking for drugs,' Mr Hamlyn-Harris said the notification stated.

Darcey-Helen was removed from her mother's care on November 7, 2017 but was returned a month later to live with her mother after Conley agreed to an intervention parental agreement.

Mr Hamlyn-Harris said when Conley's second daughter, Chloe-Ann was born in October 2018, Child Services weren't 'involved with the family' at that time.

He said Logan Hospital had raised similar concerns about Conley's lack of attachment to her second daughter days after giving birth, which seemed to be a 'pattern'.

'When they were discharged from Logan Hospital Kerri-Ann denied drug use,' Mr Hamlyn-Harris said.

'They took some comfort that intervention had been revoked by Family Services.'

Mr Hamlyn-Harris said Child Services received three notifications in early November 2019 about Conley's ability to care for her children.

'After they received those concerns a child concern report was recorded,' he said.

'In the report it was noted that a report had been received that the mother was using drugs and people frequently who were drug users were spending time at the home.

'Child Safety were sceptical about the reliability of the reports and also sceptical about the motivations of the reporter so on November 12, 2017 a decision was made that the threshold for the reporting a notification under the child protection act had not been met.'

Darcey-Helen and Chloe-Ann died 11 days after this decision was made to not further investigate.

Mr Hamlyn-Harris said the inquest will look at why Child Services made the decisions it did in relation to the care of the girls and will also look at 'better practices of how to avoid similar circumstances in the future'.

He said police had previously had 'limited involvement' with Conley before the children died 'but they had from time to time received intelligence of her drug behaviour'.

The inquest will also examine the process police go through in providing information to Child Safety about any concerns raised.

Coroner Ryan set the five-day inquest to start on April 29, 2024.

Conley, who had served three years behind bars when she was sentenced, will be eligible for parole after November 22, 2024.