A one-year-old baby drowned in the bath while her mother chatted on the phone for 47 minutes, a court has heard.
Sarah Morris' daughter Rosie died at their home in Greenfield near Holywell, Flintshire, in 2015.
Ms Morris denies manslaughter through gross negligence at Mold Crown Court.
Prosecutor Oliver Saxby QC said it was accepted she had checked on Rosie and her twin brother but that there were "prolonged periods when she was chatting away" when she did not.
He also told the jury that since Rosie's death, on 29 July 2015, Ms Morris had been unable to provide a "clear and consistent account" of the circumstances in which Rosie drowned.
The 35-year-old was talking on the phone to her partner Sarah Swindells while the twins were in the bath without baby support.
The prosecution said the phone conversation only ended when Ms Swindells suggested Ms Morris check on the children.
The jury heard Ms Morris had been given assistance from Flintshire council and had received a leaflet detailing the dangers of leaving children unattended in the bath just two weeks before the incident.
After discovering Rosie in the bath, Ms Morris rang a friend who told her to call emergency services.
However after the nine-minute call, she ran into the street screaming for help. It was a neighbour who dialled 999.
Rosie was taken to Glan Clwyd hospital in Bodelwyddan but she was declared dead at 18:39 that day.
The prosecution say Ms Morris gave various accounts to paramedics and police officers of what had happened.
When the bathroom was later examined, bath seats were found but they had not been used that day.
Mr Saxby said: "Having decided not to use them, it was even more important that she supervised the twins in the bath (and) didn't allow herself to be distracted.
"Parents make mistakes and can be distracted so that accidents happen."
However he added: "Leaving 13-month-old twins in the bath in these circumstances is gross negligence."
The trial continues.