Maternal Influenza Vaccination Tied to Reduced Prematurity

Vaccination during pregnancy may reduce odds of prematurity in periods of influenza activity

WEDNESDAY, June 1 (HealthDay News) -- Receipt of vaccination against influenza during any trimester of pregnancy reduces the likelihood of prematurity and of small-for-gestational-age (SGA) births during local and widespread influenza activity periods, according to a study published online May 31 in PloS Medicine.

Saad B. Omer, Ph.D., M.P.H., M.B.B.S., from the Emory University Rollins School of Public Health in Atlanta, and colleagues analyzed the association between maternal receipt of inactivated influenza vaccine during any trimester of pregnancy and prematurity or SGA births in 4,168 live births between 2004 and 2006. Maternal receipt of inactivated influenza vaccine was evaluated. Prematurity (gestational age of less than 37 weeks at birth), and SGA (birth weight less than tenth percentile for gestational age) were the main outcomes studied.

The investigators found that infants born during the influenza season (October to May) to mothers who were vaccinated during pregnancy were less likely to be premature compared to those born to unvaccinated mothers (adjusted odds ratio [aOR], 0.60). The correlation between maternal vaccination and reduced prematurity increased during the period with local influenza activity (aOR, 0.44), and was highest during the period of widespread influenza activity (aOR, 0.28). During the period of widespread influenza activity, newborns of vaccinated mothers had lower odds of being SGA than newborns of unvaccinated mothers (aOR, 0.31), but neither the adjusted nor unadjusted associations were significant for the period prior to influenza activity.

"This study demonstrates an association between immunization with the inactivated influenza vaccine during pregnancy and reduced likelihood of prematurity during local, regional, and widespread influenza activity periods," the authors write.

One of the study authors disclosed financial support from a research award that receives funding from the pharmaceutical industry.

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