She did everything she could to help herself and went to see 10 different health professionals.
After six months of suffering, believing she could not be the perfect mother to her newborn son, she took baby Spencer's life.
On May 20, 2022, Nguyen used parts of the six-month-old boy's toy, inserting them in his throat, causing him to suffocate and die.
Nguyen then attempted to take her own life.
Her husband, Ben Recto, found them lying in the couple's bedroom when he came home from work.
Nguyen, from Mernda in northeast Melbourne, was taken to hospital and spent weeks recovering from her injuries.
A suicide note she behind left was read to the Supreme Court on Friday, as she was convicted of infanticide and released on a three-year good behaviour bond.
The 37-year-old described her mental health battle in the letter, and asked to be buried with her son.
"This battle with post-natal depression and post-natal anxiety is so real, it's now been six months and I keep getting worse," she wrote.
Nguyen was once a bubbly, friendly person who changed dramatically after giving birth to Spencer.
She strived for perfection as a mother but felt overwhelmed and helpless.
Nguyen knew she needed help and took herself to see psychologists, GPs and to hospital after suffering from tremors.
Several health professionals asked her if she felt like harming herself or her son, and she responded no.
Justice Lex Lasry was critical of those professionals' reliance on Nguyen's self-assessments.
"Your assessment of yourself shouldn't have been relied upon," he said.
"There were other clinical signs that made it clear you were at significant risk."
Nguyen was only given the mental health treatment she needed after her son died, when she was admitted to in-patient care at a hospital psychiatric ward.
Her family want to make sure their heartbreaking experience will shine a light on a broken health care system.
"They want Spencer's death to be a learning experience for health care, that women are vulnerable after they give birth and that this was a tragedy that could have been avoided," the family's lawyer Ruth Parker said.
"She reached out for help ... and the system is not equipped and is not ready to give the kind of assistance that she needed."
Mr Recto hopes their experience will bring better awareness to the harm caused by improperly treated post-natal depression.
"I don't want Spencer's passing to not be a key lesson for families and the system," he said, in a statement to the court.
"We have experienced the loss of our first child and I really want to build awareness so that there is more support for families and new mums."
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