Scale of swine flu threat to pregnant women revealed

March 19, 2010 by Jennifer Trueland · Leave a Comment

The H1N1 virus

Women with swine flu are 13 times more likely to suffer critical illness if they are pregnant, according to a study published today.

The findings lend weight to the campaign to immunise pregnant women against the disease. Although pregnant women are offered vaccination, uptake has so far been low.

The study, published in the BMJ today, found that pregnant women, particularly those in the second half of pregnancy, were more likely than non-pregnant women to develop critical illness associated with H1N1 influenza. “Among women who developed critical illness, the outcomes were poor, including death of the mother or baby,” the researchers conclude.

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 intensive care unit in Australia or New Zealand in the winter months of June, July and 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.”

None of the women in the study had been immunised against seasonal flu, despite recommendations that pregnant women should be immunised, the authors say.

“The availability of H1N1 vaccine and antiviral treatment may modify the epidemiology and alter the course of the disease in the future,” they add.

Dr Dean Marshall, chairman of the BMA’s Scottish GP Committee, encouraged pregnant women to take up the offer of vaccination. “Uptake hasn’t been great so far. It’s the first time we’ve had a vaccination campaign aimed at pregnant women, so we knew it was going to be difficult. But this study adds to the evidence that pregnant women are at greater risk of critical illness from pandemic flu and we’re keen that as many as possible should be vaccinated.”

By 15 March 2010, under half the pregnant women (46.7 per cent) Scotland had been vaccinated against H1N1, according to estimates from Health Protection Scotland. This compares to uptake of 57 per cent for people aged 65 and over.

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