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Flu or Flu Shot During Pregnancy Won't Raise Autism Risk in Child: Study

Review of nearly 200,000 U.S. children found no good evidence of an effect, researchers say

pregnant woman

MONDAY, Nov. 28, 2016 (HealthDay News) -- Women who catch the flu or receive a flu shot during their pregnancy may rest easy knowing that neither event seems to raise their child's risk for autism.

That's the finding from a new study of nearly 200,000 children born in California between 2000 and 2012.

"This large study is reassuring for expectant mothers. The results of this study confirm that neither getting influenza during pregnancy or getting a flu vaccine in the second or third trimester is associated with risk of autism in the child," said study author Lisa Croen. She directs Kaiser Permanente's Autism Research Program in Oakland.

The study, published Nov. 28 in the journal JAMA Pediatrics, involved nearly 197,000 children born over a 10-year span. According to the researchers, 1,400 (about 0.7 percent) of the children's mothers were diagnosed with the flu during their pregnancies, and around 45,000 of the moms-to-be got a flu shot.

About 3,100 of the children went on to develop an autism spectrum disorder. However, there was no link seen between autism and maternal influenza or the mom receiving a flu shot during the last two trimesters of pregnancy, Croen and her colleagues said.

There was a "suggestion" of increased risk for autism in the child if the mom got a flu shot during her first trimester, but this statistic disappeared after the researchers further refined their analysis.

They stressed that this study was a retrospective look at data, so it can't prove or disprove any cause-and-effect relationships, but only point to associations.

Based on the findings, Croen said that "we are not recommending changes in our vaccination policy, which currently is to encourage all women to be vaccinated against the flu during their pregnancy."

Dr. Jennifer Wu, an obstetrician-gynecologist at Lenox Hill Hospital in New York City, reviewed the new findings. She said that "despite lack of evidence, many pregnant patients still worry about a link between vaccinations and autism."

On the other hand, she said, "the flu vaccine is very important for pregnant patients as they have higher risks of hospitalization and needing ventilation with flu infection. This study helps doctors to reassure their patients that flu vaccination in the second and third trimesters is safe.

"There should be some caution about giving the flu vaccination in the first trimester," Wu said, "as there was an increase in autism spectrum disorders -- which was not found to be significant."

Her advice? Women who are "planning a pregnancy may want to get the [flu] vaccine before conceiving," Wu said.

One pediatrician said more research is needed to settle the first trimester finding.

"Additional studies are needed to clarify whether or not there is an association between first trimester influenza vaccinations and later autism spectrum disorders, so that more informed recommendations can be made to pregnant women," said Dr. Andrew Adesman. He's chief of developmental and behavioral pediatrics at Cohen Children's Medical Center in New Hyde Park, N.Y.

More information

For more on the flu and pregnancy, head to the U.S. Centers for Disease Control and Prevention.

SOURCES: Jennifer Wu, M.D., obstetrician-gynecologist, Lenox Hill Hospital, New York City; Lisa Croen, Ph.D., director, Kaiser Permanente's Autism Research Program, Oakland, Calif.; Andrew Adesman, M.D., chief, developmental and behavioral pediatrics, Cohen Children's Medical Center, New Hyde Park, N.Y.; JAMA Pediatrics, news release, Nov. 28, 2016
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