2009 H1N1 influenza A and pregnancy outcomes in Victoria, Australia.

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.