With all the things women may worry about during pregnancy, doctors don’t want a case of the flu to be among them. That’s because pregnant women are more likely to suffer a severe illness from the flu and potentially life-threatening complications.

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“Pregnant women have rates of complications of flu that are comparable to people who are 65 and older,” Dr. William Schaffner, an infectious disease specialist and professor of preventive medicine at Vanderbilt University School of Medicine, told weather.com. “Those complications include pneumonia, having to be hospitalized and dying.”

“Pregnant women are very vulnerable to flu if it strikes them,” he added. “Flu vaccine provides the best protection for pregnant women and their newborn babies.”

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The contagious respiratory illness is marked by fever, chills, cough and sore throat, stuffy nose and achy muscles. Pneumonia is the most common complication of the flu for everyone, and pregnant women may also suffer from premature labor or delivery as a result of the flu, Schaffner said.

“Pneumonia in a pregnant woman is clearly life-threatening and can on occasion threaten the integrity of the pregnancy,” Schaffner said.

The Centers for Disease Control and Prevention and the American College of Obstetricians and Gynecologists recommend the flu shot for pregnant women.

“We would like every woman who’s pregnant right now in the U.S. to be vaccinated against influenza,” Schaffner said. “That’s in their best interest and in the best interest of baby that they’re carrying. And now is the time to do it. Flu is just getting started.”

Getting the flu vaccine doesn’t mean you can’t get the flu but it can reduce the severity of the illness, whether you’re pregnant or not.

“The influenza vaccine is a good but not perfect vaccine,” Schaffner said. “If you get the flu after the vaccine, you’re more likely to have a mild infection and less likely to have the severe complications.”

When it comes to pregnant women, Schaffner calls the vaccine “a twofer.” It protects the woman from the flu and later, her newborn baby from the virus for several months, notable because flu shots are not recommended for babies until they are 6 months old.

“The importance of the flu shot in pregnancy is two-fold,” Schaffner said. “It provides protection to the mom herself from influenza and its complications. Once the baby is born, some of that protection from the mom goes across the placenta, goes into the baby and helps protect the baby during the first four to six months of life.”

Young babies are at high risk of getting the flu and of suffering from complications like pneumonia, he said, urging that anyone who comes into contact with a new baby like caregivers, siblings and visitors also be vaccinated.

“Those grandparents and Aunt Susie and everyone who comes in to see the cute new baby should be vaccinated so they don’t bring the flu to the baby,” Schaffner said.

Pregnant women are at increased risk from the flu because their immune system is somewhat compromised when they are expecting, their heart is under greater stress because it is working harder and their lungs can become compressed and more susceptible to pneumonia infection, Schaffner said.

Women can get the flu shot in any trimester and the CDC says the vaccine is safe for pregnant women and their fetuses.

“That has been studied very, very thoroughly, very rigorously and everyone, the OBs, and the public health and infectious disease people are completely comfortable with that statement,” Schaffner said. “The vaccine is safe during pregnancy.”

Pregnant women who fall ill with flu symptoms are advised to call their doctor immediately. The CDC recommends that they be treated with prescription antiviral drugs.

“Getting early treatment with Tamiflu can shorten the duration of influenza and helps prevent the complications,” Schaffner said.

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