The British Medical Journal (BMJ 2010;340:c1279) just published the results of a study of women who were more than 20 weeks pregnant and suffering from 2009 H1N1 influenza in Australia and New Zealand…the results were a bit sobering.   These women were 13 times more likely to become critically ill and be admitted to hospital than non-pregnant women.

Between June 1 and Aug. 31, 2009, 209 women of childbearing age were admitted to intensive care units with confirmed 2009 A/H1N1 influenza. Of these, 64 were either pregnant or had recently given birth.  None of the women had been immunized against seasonal flu, despite recommendations that pregnant women should be vaccinated, the study authors noted.

Outcomes After Admission To Intensive Care Unit
Patient outcomes after admission to intensive care unit

Overall, seven women, or 11 per cent, died. Of the 60 births, four were stillbirths and three were infant deaths, a fetal loss of 12 per cent.  Although an adult mortality of 11 per cent seems low when compared with usual outcomes of respiratory failure in intensive care, it is high when compared with any other obstetric condition, the researchers said.  The study also confirmed previously reported risk factors for severe disease, including indigenous population status, presence of other conditions such as asthma, and obesity were associated with a worse outcome.

Gestation At Onset Of Influenza Symptoms
Gestation at onset of influenza symptoms in women, according to pregnancy status

This research offered detailed data to enhance understanding of maternal risk and outcomes for mothers and newborns. The researchers, from the Australian and New Zealand Intensive Care Influenza Investigators team, stressed that because of the small numbers in the study, there are limits to the conclusions that can be drawn from the results. Having said that though, the study went on to state that pregnant women, particularly in the second half of pregnancy, are more likely than non-pregnant women to develop critical illness associated with the 2009 H1N1 influenza. Among women who developed critical illness, the outcomes were poor, including death of the mother or baby.