Lawyer Jean-Pierre Menard, who was lending his support to Sonia Blanchette after she decided she no longer wanted to eat, said she fully understood the consequences.
Crown prosecutor Rene Verret had earlier confirmed the death without specifying the cause.
"At the opening of the next (judicial) session on March 30, we will table Madame Blanchette's death certificate and the file will end like that," Verret said in an interview.
Blanchette was to appear in court Friday to have a date set for her first-degree murder trial.
She was charged in the December 2012 deaths of Lorelie, 5, Loic, 4, and Anais, 2, after they were found dead in her apartment in Drummondville, midway between Montreal and Quebec City.
A coroner ruled the two youngest children drowned and that the oldest was killed by a combination of strangling and drowning.
Blanchette's death will result in the release of evidence presented at her preliminary hearing. It has been subject to a publication ban.
"As soon as the case is over, the publication ban falls," said Blanchette's lawyer, Marie-France Plante. "Its purpose was to prevent jury contamination."
Verret confirmed the evidence against Blanchette will become public.
"When the case is closed we will learn about the evidence presented during the preliminary hearing," he said.
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