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 Queen Elizabeth Hospital (QEH) opened in 1980, one of seven hospitals built using a material called reinforced autoclaved aerated concrete (RAAC).
The material has serious weaknesses and is deteriorating, with uncertainty over its structural integrity leading to more than £100m being spent this financial year on safety measures across the affected sites.
Mr Stewart told BBC Radio 4's Today programme: "I think people are very frustrated, they're well aware that the hospital staff inspect the hospital on a daily basis, several times a day.
"That said, we are aware of patients, for example, who are giving birth, who have asked to go to other hospitals because they're scared in case the roof might fall in on them."
The hospital's interim chief executive, Alice Webster, said while four theatres have had to be closed, "potentially" there could be problems with the ceilings in the others.
"We continue to monitor it on a daily basis," she said.
"We're making sure our theatres are functioning longer, we're functioning at weekends and trying to manage the waiting lists that way."
She added: "If we don't get a new hospital we will have to review all the services that we currently provide, but we won't be able to provide all the services that we currently do."
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Source: BBC News, 13 November 2022