Study finds H1N1 flu in pregnancy is critical risk

Pregnant women in Australia and New Zealand who had pandemic H1N1 flu were 13 times more likely to become critically ill and be admitted to hospital, researchers say.

The study, published in the British Medical Journal (BMJ), analysed data from the middle of the southern hemisphere’s 2009 winter and found that 11% of mothers and 12% of babies died after admission to intensive care with swine flu.

The findings confirm earlier research that pregnant women are at higher risk of serious complications if they get the flu.

The World Health Organisation (WHO) declared last June that the new H1N1 virus was causing the first influenza pandemic in more than 40 years after it spread around the world from Mexico and the United States in just six weeks.

The H1N1 pandemic sparked a race to develop new vaccines by drugmakers including GlaxoSmithKline and Sanofi-Aventis. But the vaccines were not ready until later in the year, and then many people failed to have the shots because of safety concerns and because the pandemic was milder then feared.

Ian Seppelt from the Australian and New Zealand Intensive Care Influenza Investigators, who led the BMJ study, noted that none of the women studied had been immunised against regular seasonal flu, despite recommendations that they should be.

Intensive care

During the study period from June 1 to August 31, 2009, a total of 209 women of child-bearing age (15 to 44) were admitted to intensive care units with confirmed swine flu. Sixty-four of those were either pregnant or had recently given birth.

Women who were more than 20 weeks pregnant were 13 times more likely to be admitted to intensive care than non-pregnant women who had swine flu, the study found.

Around 69% of the women had to be put on ventilators to help with breathing and of these, 14% needed more help with getting oxygen to reach their heart and lungs.

Overall, seven of the mothers and seven of the babies died.

“Although a mortality of 11% seems low when compared to usual outcomes of respiratory failure in intensive care ... a maternal mortality of 11% is high when compared with any other obstetric condition,” Seppelt wrote in the study.

The WHO says more than 300 million people have now been vaccinated against pandemic H1N1, and the shots, which have an excellent safety record, have proved 70-75% effective. It recommends that anyone who is offered vaccination should take it, particularly those in high risk groups like pregnant women.

So far the WHO has confirmed more than 16 200 deaths around the world from H1N1, but the real death toll — which will take at least a year to ascertain — will be far higher, as most victims will have never been diagnosed or tested.