"I came home, I was suffering ... I was a mother without a baby and it was so hard," Ms Pirko told Nine News.
"It has impacted our lives, in a dramatic and horrific way," Ms Pirko said.
The couple's paperwork went missing and a lack of funding meant there was no full-time technician responsible for the hospital mortuary.
"We trusted them to do their jobs - to find out what happened to our baby. We cannot fathom how this happened," she said.
She also questioned how their doctor, who also handled the couple's request for follow-up testing, authorised the cremation when he knew the post-mortem hadn't been done.
The cremation also robbed them of answers about why their baby developed an enlarged bladder and whether they could have more problems in the future.
The hospital has said it was an isolated case and it has since improved its processes. It is also looking to hire a full-time mortuary technician.