The body of a stillborn baby was put in a supermarket carrier bag after it was delivered and left with the parents for two hours as they waited at hospital.
The hospital said it was urgently investigating what happened
Lisa Bundock, 33, from Brighton, was 19 weeks pregnant when she found out her boy had died and delivered him at home.
The body was put in a bag when an ambulance took her to the Royal Sussex County Hospital. She said it stayed in the bag while she waited in A&E.
An NHS spokesman apologised and said an investigation was under way.
The spokesman for the Brighton and Sussex University Hospitals NHS Trust said: "We fully understand the parents' distress and do apologise on behalf of the hospital.
"We are urgently looking into the circumstances so that we can give them a full account of what happened as soon as possible."
Mrs Bundock's stillborn baby, Joe, was her fourth child. She miscarried on 29 August.
She said she had to wait in a room in A&E for two hours without being examined, and that during that time her baby was in a plastic bag on top of a cabinet in the room with her and her husband, Michael.
She also said that when she was moved to another ward, the bag was placed on a windowsill.
Joe was later placed in a special crib next to his mother, and has since been buried.
Mr Bundock, 35, said the baby boy was wrapped in a blanket and then placed in a carrier bag at their home before the couple went to hospital.
He said: "He wasn't treated like a baby at all, more like a piece of meat.
"At the time both my wife and I were deeply distressed and upset so we didn't raise our concerns."
He said his main concern was for his wife who had lost "an awful lot of blood".
Mr Bundock said: "We hope that there is an acknowledgement that serious mistakes have been made.
"There clearly needs to be more staff and better training."