The Guingans want to know if staff at Monash Medical Centre should have detected the condition that claimed the lives of baby daughters Tiana and Amelia in scans taken weeks before their birth.

They want to know if this would have meant a different outcome for their twins.

They have engaged medical negligence lawyers Slater and Gordon, who are investigating. The law firm said it expects to pursue litigation on behalf of the family.

The girls died due to Twin-to-Twin Transfusion Syndrome, a disease of the placenta which can result in one of the twins not getting enough blood while the other is overloaded with it, placing strain on her heart.

They were nearly full term on October 9, when Ms Guingan, already a mother of two young sons, felt pain she thought to be contractions.

"The doctor came in to do an ultrasound, she didn't tell me but we could see that one of the sacs, the heart wasn't beating," Ms Guingan said, speaking from her home in Melbourne's outer south-east.

"Normally when they do the ultrasound you can see a little flickering, I could see my youngest's little flickering but I couldn't see my eldest."

"I said to her 'is everything okay' because there's no heart beat and she said everything is fine."

The family alleges it was another three hours before a further ultrasound was performed and the alarm raised for an emergency caesarean section.  The parents were told one girl was gone and the second was in danger.

After waking from surgery, Ms Guingan learned Tiana was in intensive care and that the family was going to have to make an impossible decision, she said.

"All I could see was the cords coming out of her and they told me I had to decide if we want her to stay on life support because she didn't have oxygen for 25 minutes and she had severe brain damage and they told me I had to make a decision," Ms Guingan said.  "I was trying not to fall asleep because I was on morphine."

The family allege hospital staff gave them only an hour to decide.  They made the heartbreaking decision to take Tiana off life support and she slipped away the following morning.

Ms Guingan and her husband say they were called back into the maternity ward in early December and allege a specialist who reviewed their case told them the TTS was present but missed at an ultrasound taken about two weeks before the births.

They also allege the doctor told them their case should have been flagged as an emergency sooner on the day of the birth.

"It gave me closure knowing it wasn't something I did wrong but at the same time made me more angry and frustrated that it could have all been prevented if they just did their job right," Ms Guingan said.  "It wasn't just one life, it was two lives, and one life is not acceptable."

Fairfax Media has been unable to independently verify this meeting.

"Monash Health continues to offer support and extend condolences to the family and extended family on the loss of their twins babies," a spokesman for the hospital said. "Due to our commitment to patient confidentiality we're unable to comment any further."

He said the hospital was unaware of any legal action.

Anne Shortall, the head of medical law at Slater and Gordon, said she expects to pursue civil action.

"What we're investigating is whether or not this twin-to-twin transfusion that caused the death of both twins could have been picked up earlier and treated, hopefully resulting in the safe birth of both girls or at least one girl," she said.

Ms Guingan said she doesn't want another mother to experience her pain. "I want them to be aware for the next person," she said.