Before the advent of antibiotic agents, pregnancy was a
recognized
risk factor for severe complications of pneumococcal pneumonia, including
death.1 The influenza pandemic of 2009 provided a more recent reminder
that certain infections may disproportionately affect pregnant women. Are
pregnant women at increased risk for acquiring infections? Are pregnant women with
infection at increased risk for severe disease? During pregnancy, several mechanical
and pathophysiological changes occur (e.g., a decrease in respiratory volumes and
urinary stasis due to an enlarging uterus), and immune adaptations are required to
accommodate the fetus. In this article, we review and synthesize new knowledge
about the severity of and susceptibility to infections in pregnant women. We focus
on the infections for which there is evidence of increased severity or susceptibility
during pregnancy that is not fully explained by mechanical or anatomical changes,
and we discuss these infections in light of new findings on immunologic changes
during pregnancy.