"According to the CDC, there have been 20 recent H1N1 infections in pregnant women in the U.S. (15 probably cases and five confirmed cases). Of those, three women were hospitalized and one died. A woman's immune system is somewhat weaker during pregnancy. That means those who become infected with flu are more likely to develop serious complications, such as pneumonia." ([Pregnant women are at greater risk for flu] by Los Angeles Times)