Around 800 pregnant women across Tayside are putting themselves at risk from flu by failing to get vaccinated.
Mothers-to-be are being urged to get protected as they are 10 times more likely to be admitted to intensive care with flu than other women, according to evidence from the swine flu pandemic.
They are also at increased risk of dying from the flu infection.
The exact reasons are not clear, but it may be that changes to the immune system during pregnancy puts a woman and her baby at increased risk of severe infection, including an increased risk of dying.
Most pregnant women will have only mild symptoms and recover within a week.
Health professionals say the seasonal flu vaccine is very effective at protecting against the swine flu virus circulating at the moment, as well as two other types of flu.
All pregnant women are being offered vaccination against seasonal flu.
NHS Tayside said there are around 1500 expectant mothers in the region and around 800 have not come forward for vaccination.
Doctors and midwives have written to all pregnant women to urge them to get vaccinated.
