The Royal Cornwall Hospital has denied that the role of midwives is being downgraded in its maternity unit.
Six registered nurses have been appointed to fill posts traditionally occupied out by midwives.
The hospital said they would have only nursing roles and would not deliver babies.
A spokesperson for the Royal College of Midwives said it had reservations about general nurses being employed in place of newly-qualified midwives.
The midwifery body said using registered nurses was fine if it allowed midwives to spend more time with women in labour.