The Centers for Disease Control and Prevention recommends the flu shot as a priority for pregnant women because studies and history have shown they are at a higher risk for flu-related hospitalizations and death compared with non-pregnant women.
The H1N1 virus emerged in 2009 to cause a pandemic and was particularly hard on pregnant women, who were four times more likely to be hospitalized from flu than non-pregnant women. The H1N1 flu strain is the strain circulating currently among those with influenza.
The study, published in the in the journal Clinical Infectious Diseases, showed influenza vaccine effectiveness estimates among pregnant women were similar to those found in other studies, which ranged from 44 percent to 51 percent for the 2010-2012 period.
The CDC received reports this season of pregnant women with complications, officials said.
Influenza activity is widespread in most of the United States at this time and is likely to continue for the next several weeks at least, but it's not too late for pregnant women to get vaccinated and still benefit from the protection the flu vaccine can provide, the CDC said.
Vaccination not only protects the pregnant mother from flu and its complications, but also has been shown to provide some immunity to the newborn child during the first six months of their lives.