By EMILY WOODS, AAP
Police and family believe Krystal Fraser could have been murdered by her unborn baby's father, an inquest has heard.
The 23-year-old from Pyramid Hill went missing 13 years ago from regional Victoria, after discharging herself from hospital against medical advice just days before she was due to give birth to her son.
She told staff at Bendigo Hospital that she wanted to go to a party in Cohuna on June 20, 2009, but she never made it there.
Ms Fraser and her unborn son have not been seen or heard from since.
The inquest into her disappearance is examining whether Ms Fraser died, how she died and the circumstances leading up to her death.
More than 20 witnesses will give evidence over the inquest's six days.
Her sister Chantel Fraser was scheduled to appear by videolink from Queensland on Tuesday.
It comes after Ms Fraser's mother Karen told the inquest she believed her daughter may have been killed by her baby's father.
"Maybe she told someone they were the father and they didn't want to be and things got out of control and somebody accidentally hurt her," she said on Monday.
"I just can't imagine anybody hurting somebody so vulnerable."
Three men have been named as possible fathers — Peter ‘PJ’ Jenkinson, Gareth David and Tony Gatt.
Mr David, who appeared as a witness by videolink on Monday, denied he had ever had sex with Ms Fraser, saying the two were just friends.
This was despite Mr David telling police there was a chance he could be her baby's father in a 2009 police interview.
"When I look back now, I just don't think we had sex," he said.