The mistaken termination of a healthy unborn boy at Melbourne's Royal Women's Hospital is unlikely to be referred to the coroner because the baby never took a breath.

The 32-week foetus was this week terminated instead of his seriously ill twin brother in a procedure his mother agreed to on medical advice.

'Traumatised' ... The hospital aborted the wrong baby. Credit:Craig Abraham

Doctors reportedly advised the woman that one of boys, whom she had already named, had a congenital heart defect that would require years of operations, if he survived at all, the Herald Sun reported.

The mother made the heartbreaking decision to abort, but at 2.30pm on Tuesday the wrong baby was injected, terminating the healthy foetus.