The woman, a resident of the municipality of Flaach, strangled herself while in a solitary confinement cell.
She was being detained for allegedly smothering to death her two-year-old daughter Alessia and five-year-old son Nicolas on January 1st, after they had been ordered placed in a foster home, Swiss media have reported.
The children were allowed to stay with their mother for the Christmas holidays but were to return to the home while authorities clarified the role of the woman and her husband (in jail at the time of the murders), who were suspected of fraud.
The woman was subsequently detained in a psychiatric clinic before being transferred to Zurich prison in May while the investigation into the children's deaths continued.
The Zurich department of justice said in a statement on Tuesday that doctors approved the transfer.
She was placed under tight surveillance and after she showed signs of preparing to commit suicide she was moved to a high security cell amid other preventive measures.
These measures were lifted after no concrete sign of suicide emerged, the department said.
The woman's parents maintain she was suffering from isolation, 20 Minutes newspaper reported.
She had written them a letter that said “if I don't return to the clinic, I will not live very long,” the daily said.
Her father alleged in an interview with 20 Minuten newspaper that his daughter had attempted suicide twice in the Zurich prison.
Authorities made errors “clearly yes” that led to her suicide, he said.
He maintained that his daughter failed to receive the therapy she needed.
“Someone who is so traumatized cannot be easily isolated and left to themselves.”
Experts this week told Tageschau, the German-language public affairs TV programme broadcast by SRF, that Switzerland has a problem with pre-trial detention, when defendants can be kept in solitary confinement for 23 hours a day.
Such confinement can be very distressing, Thomas Meier, chief physician of St. Gallen's cantonal psychiatric services, told the programme.
"And if you do not know how long the detention will last, this may lead to suicidal behaviour and suicide attempts."
An average of five people in pre-trial detention die each year in Switzerland, leading some experts to call for criteria for solitary confinement to be reconsidered.