Women in Australia and New Zealand were 13 times more likely to be hospitalised if they were more than 20 weeks pregnant, a BMJ study found.
Results showed that 11% of mothers and 12% of babies died as a result of being admitted to intensive care with swine flu. Of 64 pregnant women admitted to hospital with swine flu, 44 (68.7%) of the women had to be put on ventilators to assist with breathing. Nine of these women (14.1%) needed further assistance to help oxygen reach their heart and lungs.
Authors identified the small numbers included in their research as a limitation to the study.
But they said the research is in line with existing data that show pregnant women are at a higher risk of developing influenza complications.
The authors highlight the fact that none of the women in the study had been immunised against seasonal flu, despite recommendations that pregnant women should be immunised.