Increased Preterm Deliveries in Pregnant Women Hospitalized for Flu

By David Douglas

January 14, 2020

NEW YORK (Reuters Health) - Among findings in pregnant women hospitalized for influenza in high-income countries is a substantially higher prevalence of preterm deliveries, according to an international group of researchers.

Writing in the Journal of Infectious Diseases, Dr. Fatimah Dawood of the Centers for Disease Control and Prevention, Atlanta, Georgia, and colleagues note that pregnant women are hospitalized for flu more often than their nonpregnant peers and the general population. But data on outcomes are largely limited to pandemics.

To investigate, the team examined 2010-2016 health records from Australia, Canada, Israel and the United States. They identified more than 18,000 pregnant women hospitalized for acute respiratory infection or febrile illness (ARFI) and influenza-associated ARFI.

Of 18,048 ARFI-coded hospitalizations, 1,064 (6%) included RT-PCR testing for influenza viruses within three days of admission. Influenza vaccination uptake was low (16%) in the tested patients, but this varied from 6% in Australia to 50% in the US.

Overall, 614 women (58%) were influenza-positive. Most of this group (67%) were in the third trimester, and 20% had underlying conditions.

The majority of the influenza-positive group (82%) were still pregnant at the end of the hospital stay. Of the 110 hospitalizations that resulted in deliveries during the stay, 101 (92%) were singleton gestation deliveries of live births with available outcome data.

Up to 34% of these were preterm deliveries. This proportion, say the investigators, is "substantially higher than the estimated baseline preterm birth prevalence of 9% among the general population of pregnant women in high-income countries." There were no maternal deaths, although 5% of hospitalizations required intensive care.

Summing up, Dr. Dawood told Reuters Health by email, "We found that the majority of pregnant women who were hospitalized with fever or respiratory illness during six influenza seasons were previously healthy and had not received the current season's influenza vaccine."

"Multiple studies," she added, "have demonstrated that influenza vaccination during pregnancy provides protection against influenza to both mothers and their young infants during the first few months of life, and influenza vaccines are recommended for pregnant women in any trimester of pregnancy. Our study highlights the need for ongoing efforts to improve influenza vaccine uptake among pregnant women."

SOURCE: Journal of Infectious Diseases, online December 26, 2019.