Pregnant women with influenza are more likely to experience complications, but how this affects infants is unclear. A new Birth Defects Research study uncovers the potential risks to infants.

The study included 490 pregnant women with influenza, 1451 women without influenza with pregnancies in the same year, and 1446 pregnant women without influenza with prior year pregnancies. Women with 2009 H1N1 influenza admitted to an intensive care unit were more likely to deliver preterm infants, low birth weight infants, and infants with low Apgar scores than women in the other groups.

Women with influenza who were not hospitalized, as well as hospitalized women not admitted to the intensive care unit, did not have significantly elevated risks for adverse infant outcomes.

“The message of this work is particularly timely in the midst of the current influenza season. Our study found that severely ill women with 2009 H1N1 influenza during pregnancy were more likely to have adverse birth outcomes—such as their baby being born preterm or of low birth weight—than women without influenza,” said senior author Dr. Sonja Rasmussen, of the University of Florida. “These findings support the importance of pregnant women receiving the influenza vaccine and of prompt treatment with antiviral medications for pregnant women suspected of having influenza.”