In response to a new study that found a weak, inconclusive link between the flu shot and miscarriage, the American College of Obstetricians and Gynecologists on Wednesday repeated its recommendation that pregnant women get the vaccine, because it has been shown to save mothers and babies from illness and death.
“Influenza vaccination is an essential element of prenatal care because pregnant women are at increased risk of serious illness and mortality due to influenza,” ACOG said in a statement. “In addition, maternal vaccination is the most important strategy to protect newborns because the vaccine is not approved for use in infants younger than six months.”
The U.S. Centers for Disease Control and Prevention, which funded the new study and had a presentation on the data in June 2015, posted a website update that said it has “not changed the recommendation for influenza vaccination of pregnant women.”
Many published studies have shown the flu vaccine is safe and effective during pregnancy, although data are limited for the first trimester. The new work, led by vaccine researchers at Marshfield Clinic Research Institute in Wisconsin, is the first to find a possible link to miscarriage, and the authors say the finding could be just by chance. The study showed only an association, not a causal link.
The study compared 485 women who miscarried with an equal number who did not miscarry during the flu seasons of 2010-11 and 2011-12. The odds of a miscarriage were higher for women who got a flu shot within the preceding 28 days — but only if they also got the vaccine in the previous year, before becoming pregnant. The results were published in the September issue of the journal Vaccine.
The study had limitations, the CDC said, including small numbers of participants, and the fact that it couldn’t estimate the actual risk of a miscarriage after vaccination.
The CDC noted that an ongoing study is looking at miscarriage risk among women who were eligible to get the flu shot during the 2012-13 and 2014-15 flu seasons, but the results are not expected until late next year.