Preventing Preterm Births with a Flu Shot

Author: Laura Enderle, Associate Editor

Public health experts have uncovered yet another benefit of influenza vaccination for expectant mothers. According to a new study, pregnant women who receive the vaccine are less likely to deliver prematurely or give birth to babies of low birth weight. 
 
The mitigating effect is strongest for babies born during peak flu season, which usually occurs in January and February, researchers reported in “Maternal Influenza Immunization and Reduced Likelihood of Prematurity and Small for Gestational Age Births,” an article published in the May 2011 issue of PLoS Medicine.
 
Preterm births have been associated with a maternal history of influenza, and vaccination during pregnancy has been shown to protect both mother and baby from contracting the virus. But few studies have investigated whether that protection translates to a lower risk of preterm delivery or low birth weight, the authors noted. 
 
To answer that question, they examined data on 4168 Georgia mothers who gave birth between June 2004 and September 2006. Of those women, 14.9% had been vaccinated during pregnancy, 10.6% delivered infants who were premature (born before 37 weeks of gestation), and 11.2% gave birth to babies who were small for gestational age (below the 10th percentile for weight, height, or head circumference). 
 
Pregnant women who received the vaccine and gave birth during the same flu season were 40% less likely to deliver prematurely. When reports of flu activity were widespread, vaccinated mothers were 72% less likely to deliver premature infants than unvaccinated mothers. Babies born during peak flu season to vaccinated mothers were also 69% less likely to be small for gestational age.
 
The authors concluded that “although the etiology of prematurity is complex and not completely understood, our results suggest that at least a fraction of preterm births may be preventable through maternal influenza vaccination.” 
 
Gearing up for next season 
Although the 2011-2012 flu season is still months away, women who are newly pregnant or become pregnant during the summer months will be thinking ahead, and pharmacists should be prepared to address their concerns. The Centers for Disease Control and Prevention, the American Academy of Pediatrics, the American College of Gynecologists and Obstetricians, and the March of Dimes all recommend that pregnant women receive a flu vaccination.
 
The following resources are available to help pharmacists provide women with counseling and education about safety and effectiveness of flu vaccines during pregnancy: 
 

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