BACKGROUND: Pregnant women have been identified as a group at risk of increased 
morbidity and mortality associated with the pandemic H1N1 influenza A 2009 
(H1N1/09) outbreak.
METHODS: Six hospitals in the state of Victoria, Australia, contributed 
retrospective and prospective demographic and clinical data, reason for 
admission data, and maternal and fetal outcome data for women with 
laboratory-confirmed H1N1/09 admitted to the hospital from 20 May 2009 through 
31 July 2009.
RESULTS: Forty-three cases were reported during the study period, including 8 
intensive care unit admissions, 1 maternal death, 2 fetal deaths, and 1 neonatal 
death. The most common reason for admission was uncomplicated influenza-like 
illness. Patients hospitalized for uncomplicated influenza-like illness had a 
length of stay significantly less than those with confirmed pneumonia. 
Thirty-six percent of women delivered during the hospitalization. Of the women 
delivering before 37 weeks' gestation, almost all had pneumonia. Almost half of 
our case series had no other comorbidity, a large proportion (77%) of women 
received antivirals, and 56% received antibiotics. The incidence of 
hospitalization was estimated at 0.46% (95% confidence interval, 0.31%-0.66%) of 
all 6094 pregnant women in the third trimester during the 3-month study period. 
The incidence of hospitalization in the second trimester was estimated at 0.21% 
(95% confidence interval, 0.11%-0.36%).
CONCLUSIONS: This case series confirms a high number of complications in 
pregnant women due to pandemic H1N1/09. Many of these women had comorbidities, 
although almost 50% of the women in this case series who required 
hospitalization did not have an additional risk factor other than being 
pregnant.