WEDNESDAY, May 11 (HealthDay News) -- Having the flu during
pregnancy isn't associated with a heightened risk of autism or
developmental delay in children, although having a fever during
pregnancy might be.
And giving birth by Cesarean section isn't associated with
autism in offspring, but having diabetes or high blood pressure or
being obese while pregnant seems to be.
Those are the findings of several new studies that sought to
uncover what factors during pregnancy may have an impact on the
risk of autism in children. The research was presented Wednesday
during a press conference at the International Meeting for Autism
Research (IMFAR) in San Diego.
About one in 110 U.S. children have an autism spectrum disorder,
a neurodevelopmental condition characterized by problems with
language, communication and social functioning, as well as
repetitive or restrictive behaviors. Many children with autism also
have other conditions, including epilepsy, anxiety disorders and
Recent research has found that the diagnoses of autism is on the
rise, some of which might be attributable to greater awareness and
increased availability of autism services, experts said. Still
other research suggests the actual incidence of autism is rising as
"Autism is an incredibly complex disorder than now affects nearly 1 percent of children," said IMFAR President David Amaral.
The cause of autism is unknown, although some research,
including the papers presented at IMFAR, hint at some maternal
factors that might contribute to a child developing the
In the first study, researchers looked at data from research on
1,000 kids taking part in the population-based Childhood Autism
Risks from Genetics and Environment (CHARGE) Study, which included
462 with an autism spectrum disorder, 136 with other development
disorders and 265 typically developing kids between 2 and 5. The
researchers also examined mother's reports of influenza or fever
Researchers found no link between autism or other developmental
delay and the flu during any trimester of pregnancy.
But in a weighted analysis, the mothers of children who were
diagnosed with an autism spectrum disorder were nearly twice as
likely to report having a fever during pregnancy than mothers of
kids without autism, said study co-author Irva Hertz-Picciotto,
deputy director of the University of California, Davis's MIND
Institute (Medical Investigations of Neurodevelopmental
The risks were particularly elevated when mothers reported
having a fever during the 2nd trimester.
Prior research has suggested an association between viral
infections during pregnancy and autism. Yet researchers believe the
mother's inflammatory response to the virus, rather than any
particular virus itself, influences the child's brain
"These results add to a growing body of evidence that maternally mediated inflammation might be part of the mechanistic pathway leading to autism," Hertz-Picciotto said.
The researchers stressed, however, that the findings were
preliminary and that the association did not reach statistical
significance in an analysis where they did not apply the sampling
Along that same vein, another study to be presented at the
meeting by researchers from Denmark analyzed samples of amniotic
fluid collected from pregnant women in Copenhagen since 1982. Some
of the women's children were later diagnosed with autism.
The study found no differences in hospitalizations for
infections during pregnancy, but they did find that the mothers of
autistic kids were more likely to have elevated levels of certain
inflammatory markers -- specifically, a cytokine called TNFa. For
reasons not well understood, the inflammatory markers were
particularly high in the mothers of girls with autism.
"Overall, findings from our study not only support the idea that immune dysfunction plays an important role in autism, but also confirm that this is happening actually before birth," the authors wrote.
In a third study, which also drew from data from the CHARGE
Study, researchers looked at mothers who had diabetes (Type 2 and
gestational), chronic hypertension and pre-pregnancy obesity.
The study found that the children of mothers with those
conditions were significantly more likely to have autism or another
"For mothers with at least one of the three conditions, their children had a 60 percent increased risk of autism and for developmental delays, there was a 150 percent increased risk," Hertz-Picciotto said.
Researchers also noted that children of diabetic mothers also
tended to have poorer expressive language skills whether the kids
had autism or not.
A fourth study, which looked at Cesareans and autism, also used
data on about 500 kids with autism and 300 without autism from the
The study found no link between birthing method and autism.
However, having an emergency C-section after a difficult labor
-- including prolonged labor, membrane rupture or infection of the
amniotic cavity -- was associated with a heightened autism risk in
Yet when researchers controlled for other factors, such as
maternal age, pre-eclampsia and diabetes, that are associated with
heightened autism risk, the mode of delivery was no longer
The good news is that many of the factors described in the three
studies are "modifiable," meaning that if they're confirmed to be
risk factors for autism, it may be possible to alter them,
"We'd like to be able to intervene and potentially prevent autism in the future," she said.
Experts note that research presented at meetings has not been
subjected to the same type of rigorous scrutiny given to research
published in peer-reviewed medical journals and should be
National Institute of Neurological Disorders and
Stroke has more on autism.
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