Days after attending baby scans with her partner, Kardell Lomas' body was found in the boot of an abandoned car.
The 31-year-old was seven months pregnant.
Four years later, ex-partner Traven Lee Fisher was asked to enter a plea for murder in Brisbane Supreme Court.
"I am not guilty of murder. I am guilty of manslaughter," he said tearfully on Wednesday.
Fisher, 39, had been in a tumultuous relationship with Ms Lomas for 12 months and was the father of their unborn child.
On December 8, 2019, neighbours heard an argument at the couple's Ipswich property, west of Brisbane.
"Get up you dog, get up," Fisher was heard saying.
The next day Fisher asked a friend to help him "move something".
Asked what it was, Fisher replied: "It's Kardell. She's inside. She's OD'd. She has taken heaps of pills."
The friend said they should call an ambulance.
Fisher said it was "too late for that".
Ms Lomas had likely been in the car boot for 48 hours.
Her body was too decomposed to establish a cause of death.
However, evidence suggested it was from choking, crown prosecutor Todd Fuller said.
"I describe the crime as horrific in nature," he said.
Fisher most likely killed Ms Lomas on December 8, when neighbours overheard the argument, Mr Fuller said.
Two days earlier, Fisher and Ms Lomas had happily attended Ipswich hospital for baby scans.
However, neighbours said Fisher was abusive to Ms Lomas and the pair were argumentative on regular basis.
Police found her body in one of four broken down cars on the Ipswich property on December 10, following an anonymous call.
Fisher made a calculated attempt to distance himself from the killing, Mr Fuller said.
On December 9, he sent messages to relatives asking to let him know if they had seen Ms Lomas.
Fisher also sent a message to Ms Lomas' phone asking "why she always takes off when she is the only one he ever loved".
He later told police Ms Lomas had a history of staying with friends, sometimes for up to a month.
Fisher has been in custody for 1182 days, but only indicated he would plead guilty to manslaughter - not murder - last week.
Relatives read heartbreaking victim impact statements, detailing how their family had been destroyed after Fisher disposed of Ms Lomas "like rubbish in a bin".
Tensions boiled over after Ms Lomas' brother Adair spoke.
"I hope you suffer in a dark hole after what you did to my sister. Own it, you c***," he said before challenging Fisher, prompting a court adjournment.
Ms Lomas' aunt Shirley Lomas later apologised.
"Hate is a wasted emotion," she said.
Fisher had previously been declared a dangerous prisoner after a 2004 jail sentence for offences including rape.
He has also pleaded guilty to destruction of an unborn child and interfering with a corpse.
Justice Peter Davis has reserved his decision on sentencing.
