Doctors identified a Victorian mother was probably suffering from a depressive illness seven days before she killed one of her twin babies and seriously injured the other.
The mother scored 17 in a postnatal depression screen test in which a score of 13 or above indicates depression may be present, but at the time she was screened appeared "happy and chatty", an inquest has heard.
The mother, her husband and the couple's twin daughters attended a clinic for unsettled babies a week before one of the babies died in April 2012.
The doctor they saw, Anne Dawson, told a coronial inquest into the baby's death that it is not uncommon for a parent to have a score greater than or equal to 13 when attending the clinic because of its nature.
She said that because the mother, who cannot be named, answered positively to a question relating to whether she considered self-harm - her answer was "hardly ever" - she probed her more about potential risk.
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But when asked if she felt she might harm herself or her babies, the mother said she did not.
The couple had attended the hospital a month earlier and seemed to be improving, Dr Dawson said.
They had a "happy and chatty demeanour" at the April 19 appointment, she told State Coroner Ian Gray.
One of the babies died in hospital on April 26 after her father discovered she was unresponsive and was having trouble breathing.
A post-mortem examination found the injuries to the baby girl's brain, body and ribs were not all inflicted at the same time and were not accidental.
The mother last year pleaded guilty to infanticide - an offence which applies when a mother kills her infant while the balance of her mind is disturbed.
She also pleaded guilty to a count of recklessly causing serious injury relating to injuries sustained by the other twin and was sentenced to a 12 month community corrections order.
An inquest is being held to examine the role of healthcare providers.
Dr Dawson told the inquest on Tuesday that when she met the family she did not consider there to be any risk that either baby was being abused.
"It came as quite a big surprise to me when I heard of the tragedy," Dr Dawson said.
The inquest continues.
