When Pregnant, Flu Shots Are Needed Sooner Than Later

A new study suggests that influenza infection during pregnancy may result in an increased risk of pregnancy loss and a reduction in birthweight.

This study published by The Lancet on October 29, 2020, provides data underscoring the potential importance of flu vaccination in pregnant women. The new study found women had a 0·7–0·9% risk of influenza per month of pregnancy during the influenza season.

And antenatal influenza was associated with increased risk for some adverse pregnancy outcomes.

Furthermore, flu illness during pregnancy was associated with a reduction in the average birth weight of full-term newborns and an increased risk of late pregnancy loss, which is defined as pregnancy loss after 13 weeks gestation.

In addition, women with respiratory illness symptoms who had fever were found to have an increased risk of preterm birth.

Another finding of this study was that pregnant women had the highest incidence of flu infection during their first trimester, and the risk of having influenza during pregnancy increased with each month that women were pregnant during the influenza season. 

These findings suggest it is best for pregnant women to be vaccinated either before flu viruses begin circulating in places with distinct influenza seasons or as early in pregnancy as possible in places with year-round influenza circulation to maximize the protection of mothers and their babies throughout pregnancy.

It’s well established that pregnant women are at higher risk of severe illness associated with flu illness, there has been less information about the impact of flu illness in pregnant women on pregnancy outcomes, states the US Centers for Disease Control and Prevention (CDC).

This study included 11,277 pregnant women from India, Peru, and Thailand during the 2017 and 2018 flu seasons. Only 13% of study participants had been vaccinated against influenza.

In the USA last flu season, about 60% of pregnant women were vaccinated, but that proportion is much lower in some other parts of the world. 

The CDC recommends pregnant women receive a flu shot during any trimester of pregnancy. But not the nasal spray flu vaccine. For more information on influenza vaccines and pregnancy, visit the CDC website.

PrecisionVaccinations publishes research-based news.