According to Victoria Police, a family member had raised the alarm and emergency services visited the Reservoir house at around 11am on Monday.
Three other children were at home at the time but were not harmed.
The woman, named by ABC News as Umal Sharif Abdurahman, appeared in court today and was charged with one count of murder.
In court, Detective Senior Constable Jennifer Booth said the baby was found with what appeared to be a single knife wound in the throat.
The detective said the woman had a psychiatric illness and significant mental health issues.
Detective Senior Constable Booth also told the court that Ms Abdurahman allegedly called her husband at 11am saying “I’ve done something to the baby," The Australian reports.