Influenza
Pregnant women are at increased risk for severe illness from influenza virus infection.
Cardiopulmonary adaptive changes occurring during pregnancy, such as increased
heart rate and stroke volume and reduced pulmonary residual capacity, may increase
the risk of hypoxemia and contribute to the increased severity. During the pandemic
of 1918, maternal mortality was 27% (50% when influenza was complicated by pneumonia),
and during the pandemic of 1957, 50% of deaths among reproductive-age
women occurred among those who were pregnant.2 During the 2009 H1N1 influenza
A pandemic, pregnant women were generally at increased risk for severe disease,
including disease leading to hospitalization, admission to an intensive care
unit, or death, as compared with nonpregnant women and the general population.3
In the United States, 5% of all deaths from pandemic influenza were among pregnant
women, although pregnant women represent only about 1% of the U.S. population.
4 Higher rates of hospital admission and medical encounters for pregnant
women with confirmed or suspected influenza, as compared with the general population,
and a greater severity of disease during late pregnancy were also found in