Thursday, 16 June 2011

Flu shot lowers risk for premature delivery

Getting a flu shot during pregnancy appears to offer some protection from premature births and low birth weight babies.

Infections during pregnancy have the potential to adversely impact birth outcomes. To evaluate the association between receipt of influenza vaccine during pregnancy and prematurity and small for gestational age (SGA) births, researchers looked at data on nearly 4,326 births between June 2004 and September 2006 in United States (Georgia). About 15 percent of the women received a flu shot during pregnancy.

It was found that pregnant women who received the vaccine and who gave birth during the assumed flu season (from October through May) were 40 percent less likely to have a baby born prematurely, that is, before 37 weeks' gestation. Women who gave birth when there were some, but not widespread, reports of flu were 56 percent less likely to have a premature baby than unvaccinated women. During peak flu season, generally January and February, pregnant women who got the flu shot were 72 percent less likely to deliver prematurely.

The study also found a slight association between flu vaccine and protection from small for gestational age babies (a birth weight, head circumference or length in the bottom 9 percent) during peak flu season, but not at other times. Babies born during peak flu season to mothers who were vaccinated against flu were 69 percent less likely to be small for their gestational age, the researchers found. Outside flu season, no association was found between premature births and flu vaccination.

As an observational study, the work can only show there is an association between maternal immunizations with inactivated influenza vaccine during pregnancy and reduced risk of prematurity, and cannot demonstrate there is a causal link.

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