Study reveals flu vaccine helps expectant mothers prevent poor birth outcomes

Published on Friday, February 1, 2019

By: Kate Royals

Getting a flu shot is important for everyone, but a recent study reveals how crucial the vaccination is for expectant mothers and their babies.

A study that appeared in the journal Birth Defects Research shows pregnant women with the flu who are hospitalized in an intensive care unit are more likely to have poor birth outcomes, such as low birth weight and low Apgar scores, which reflect a baby’s general condition at birth.

The study examined data on outcomes of infants born to pregnant women with the 2009 H1N1 strain of influenza from April to December of the same year.

The study results are not surprising to Dr. April Palmer, professor of pediatric infectious diseases at the University of Mississippi Medical Center.

“Women who are pregnant are at higher risk of getting severe complications from influenza” due to compromised immune systems during pregnancy, Palmer explained, which is why pregnant women are especially encouraged not to miss their flu shot.

Unlike Zika, the flu virus itself is not a teratogen, or an agent that can cause a birth defect. But secondary problems from getting the flu can negatively affect pregnant women and their babies. This can be seen most in pregnant women who are hospitalized and admitted to the ICU, according to the study.

“When it comes to the flu infection, a pregnant woman might get a more severe reaction to the flu infection because her immune response is not as good as when she’s not pregnant, and then she’s carrying a baby, so two people are at risk,” said Dr. Joyce Olutade, assistant professor of family medicine and medical director for Student and Employee Health at UMMC.

Like with non-pregnant adults, receiving the flu vaccine can decrease the severity of the illness.

“Getting immunized prevents you from getting a severe infection and from hospitalization, and even if you are hospitalized (for the flu), it decreases the severity of it so you’re less likely to be in the ICU,” Olutade explained.

Women with severe flu were more likely to have poor outcomes than women with less severe illness or who did not get the flu, according to the study. Those who were admitted to the ICU were “more likely to deliver preterm infants, infants with LBW (low birth weight), and infants with Apgar scores” less than or equal to six. Scores can range from zero to 10.

In addition, the flu shot is believed to extend extra protection to the baby, Olutade said, which is especially important if the baby is born during flu season.

“The antibodies that the mother would’ve generated after she received the flu vaccine would then be passed on to her baby,” Olutade said.

Flu activity in the United States increased in January, and children ages 4 and under have been hospitalized more than any other age group. The predominant flu strain circulating this season is H1N1, which has a tendency to affect children, according to the Centers for Disease Control and Prevention.

The two major contraindications for receiving the flu vaccine while pregnant are if a woman has developed Guillain-Barre syndrome after a previous flu shot or if she has had a severe anaphylactic reaction to the vaccine.

But misconceptions in the public often lead pregnant women to think they don’t need a flu vaccine.

“Some misperceptions include one, that the flu shot causes the flu, and two, that the flu shot is contraindicated during pregnancy . . . or may cause harm to moms or babies during pregnancy,” said Dr. Michelle Owens, professor of obstetrics and gynecology. “The flu shot is protective to moms and their unborn babies and has not been associated with miscarriage, birth defects or fetal harm.”

Olutade said another misconception is that the flu shot contains the live flu virus: Only the nasal spray flu vaccine contains live, but weakened, viruses and is not recommended for pregnant women and children under 2 years of age. She said the shot contains the inactivated virus.

While the CDC recommends receiving a flu vaccine by the end of October, the shot can be beneficial as long as the virus is still circulating. The flu season normally ends on March 31.

If a pregnant woman does get the flu, Tamiflu is safe and recommended during pregnancy, according to Owens. The woman should be evaluated as soon as possible and limit her exposure to other pregnant women.

Owens recommends additional preventive measures for avoiding the flu, such as frequent hand washing, wearing a mask when feeling sick or with symptoms of an upper respiratory infection, and avoiding touching your face.

The critical step is getting vaccinated.

“The best course of action (against negative outcomes for expectant mothers) is prevention,” Olutade said.