Patients have been asking to go to other hospitals rather than one where the ageing roof is being held up by more than 2,400 wooden and steel posts.
The Queen Elizabeth Hospital in King’s Lynn has already had to close four of its seven operating theatres because of concerns the ceiling could collapse.
Alex Stewart, head of Healthwatch Norfolk, said some pregnant women have asked to go to other hospitals.
The trust is hoping it will be one of eight in England to get a new hospital.
The Queen Elizabeth Hospital (QEH) opened in 1980, one of seven hospitals built using a material called reinforced autoclaved aerated concrete (RAAC).