Only one death occurred among pregnant women who sought early treatment, the study found.
The researchers also found that more deaths -- more than 64 percent -- occurred in the third trimester of pregnancy, compared to the second trimester (almost 27 percent) or the first trimester (about 7 percent).
Dr. John Carpenter, division director of infectious disease at Scott & White Healthcare in Temple, Texas, said part of the reason why women may have more trouble with flu as they get farther along in their pregnancies is that the uterus is pushing on the diaphragm, making breathing a little bit harder, and making it more difficult to push out a good cough.
"While you're pregnant, be especially alert for respiratory illnesses," advised Carpenter. He said that antiviral medications, such as Tamiflu, can be given during pregnancy.
Rasmussen agreed that drugs such as Tamiflu can be given during pregnancy, and there are no known serious risks to mother or baby from these medications.
The bottom line, said Rasmussen, is that "early treatment makes a difference in complications and mortality."
Carpenter also advised getting a flu shot before getting pregnant and to avoid people with respiratory illnesses during your pregnancy.
While Rasmussen said the CDC can't predict whether the H1N1 virus will be a big threat again, it is already being included in this year's seasonal flu vaccine. And, she said, if women haven't gotten a flu vaccine prior to pregnancy, they can get one at any time during their pregnancy.
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