Throughout her pregnancy with Tahi, and also while she carried her other children, she drank excessively at least once or twice a week. On at least one occasion she drank to the point of vomiting.
On the day before Tahi died, she drank throughout the day while breast-feeding her son intermittently.
In a written response to the Herald, Ms MacKenzie said CYF had been involved with Tukiwaho in 2008 after concerns about her two eldest children.
At that time, CYF was also advised of Hoani's death.
"CYF worked closely with the wider whanau to ensure supports were in place for the mother.
"We ceased our involvement once we believed she had the support she needed and was coping," Ms McKenzie said.
CYF was not alerted to the fact Tukiwaho had given birth to Tahi in late 2010, she said.
In 2007, CYF had previously taken into its custody two children which the boy's father had with another woman.
After Tahi's death, two of his siblings were taken into the care of members of Tukiwaho's family, as was a third child she gave birth to later that year.
Ms MacKenzie described Tahi's death as "tragic" and has launched an "immediate investigation" at Ms Bennett's request.
"Evidence which has emerged during the course of the trial into Tahi Edwards' death has raised concerns for all of us."
CYF would be investigating its own practice and talking with others involved with the family "to get to the bottom of this".
Tukiwaho will receive counselling for alcohol and be eligible for parole after completing one third of her 25-month sentence.
