Dr. Denise Jamieson of the CDC said the flu could increase the risk of miscarriage and that the baby may be born too early or too small. Pregnant women also have their own risks if they get sick.
"Once they do get the flu, they're more likely to have severe complications, including hospitalization and death," Jamieson said in a statement.
Jamieson said decades of experience show the flu vaccination is safe for the mother and the unborn child.
Women can be vaccinated at any time in the pregnancy, but the best time is as soon as the vaccine is available, Jamieson recommended.
The CDC recommends everyone who is at least six months of age should get a flu vaccine this season. Groups of people considered high priorities for flu vaccinations include:
-- People at high risk of developing serious complications like pneumonia if they get sick with the flu.
-- People with certain medical conditions, including asthma, diabetes and chronic lung disease.
-- Pregnant women.
-- People age 65 and older.
-- People who live with, care for or have contact with the elderly, the very young, the chronically ill or those with a serious illness such as cancer.