Women with swine flu 13 times more likely to suffer critical illness if they are pregnant, study finds

The authors conclude that 11% of mothers and 12% of babies died as a result of being admitted to intensive care with swine flu. However they emphasise that given the small numbers included in their research, there are limits to the conclusions that can be drawn from the results.

It has already been established that pregnant women are at a higher risk of developing influenza complications. The recent swine flu pandemic was the first "to occur in an era of modern obstetric and intensive care management," says the study.

The research describes what happened to pregnant women with swine flu who were admitted to intensive care units (ICU) in Australia and New Zealand during the winter of 2009.

The authors, led by Dr Ian Seppelt from the Australian and New Zealand Intensive Care (ANZIC) Influenza Investigators in collaboration with the Australasian Maternity Outcomes Surveillance System, assessed the data relating to all women with swine flu who were pregnant or who had given birth in the last 28 days and were admitted to an ICU in Australia or New Zealand between 1 June and 31 August 2009.

During the study period, 209 women of child-bearing age (15 to 44) were admitted to an ICU with confirmed swine flu. Sixty-four of these (30.6%) were either pregnant or had recently given birth, 57 were admitted to an ICU in Australia and 7 to an ICU in New Zealand.

The results show that women who were more than 20 weeks pregnant were 13 times more likely to be admitted to an ICU than non-pregnant women who had swine flu. Forty-four (68.7%) of the women had to be put on ventilators to assist with breathing and of these, nine women (14.1%) needed further assistance to help oxygen reach their heart and lungs.

Overall seven (11%) of the mothers and seven (12%) of the babies died and Dr Seppelt argues that "although a mortality of 11% seems low when compared to usual outcomes of respiratory failure in intensive care … a maternal morality of 11% is high when compared with any other obstetric condition."

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.

In an accompanying editorial, Dr Stephen Lapinsky from the Mount Sinai Hospital in Toronto, applauds the ANZIC team for their foresight and planning in investigating how swine flu affected pregnant women and those who recently gave birth.

He says the study "provides detailed data to enhance our understanding of maternal risk as well as the maternal and neonatal outcome."