Getting the flu when a woman is not pregnant is a normal thing that poses no marked threat to the woman. The moment a woman falls pregnant, this assurance goes away because with pregnancy comes a low immunity. The body perceives the pregnancy as an alien invasion, therefore, going into
the high alert mode.
According to the CDC, "Changes in the immune system, heart, and lungs during pregnancy make pregnant women more prone to severe illness from flu, including illness resulting in hospitalization. Flu also may be harmful to a pregnant woman's developing baby. A common flu symptom is a fever, which may be associated with neural tube defects and other adverse outcomes for a developing baby."