If a mother has an infection or the flu during pregnancy, can it
raise the risk of autism for her child? A new study out of Denmark
suggests that the answer is "probably not" and "maybe" and that the
issue definitely needs more study.
"Overall, we found little
evidence that various types of mild common infectious diseases or
febrile episodes during pregnancy were associated with ASD/infantile
autism (autism spectrum disorders)," the study authors wrote.
But
they also say their data suggest there are three scenarios in which
there might be an increased risk of the child developing autism. If the
mother had the flu, there was "a two-fold increased risk of infantile
autism; if the mom had "prolonged episodes of fever" (lasting a week or
more), the risk goes up threefold; "and use of various antibiotics
during pregnancy were potential risk factors for ASD/infantile autism."
But
the study authors also concede that the results may be skewed by
multiple testing, contributing to the potential for "chance findings."
The study
These
results of this study -- published Monday in Pediatrics, the journal of
the American Academy of Pediatrics -- are based on researchers
interviewing the mothers of 96,736 children born in Denmark between 1997
and 2003.
These women were asked nearly 200 questions in phone
interviews around the 17th week of pregnancy, the 32nd week of pregnancy
and six months after giving birth, long before any child could have
been diagnosed with autism. This aimed to eliminate "recall bias," which
can occur in studies where subjects self-report on their health. These
women were asked whether they had any infections or episodes of fever
and for how long, and whether they had taken any antibiotics.
The results
Among
the over 96,000 children born, 976 were later diagnosed with autism
spectrum disorders. The main signs and symptoms of autism involve
difficulties with communication, social interactions and repetitive
behaviors. According to the latest statistics from the U.S. Centers for
Disease Control and Prevention, one in 88 children currently is
diagnosed with autism, including one in 54 boys.
The study authors
themselves note that a recently published Swedish study, which used
inpatient hospital register data, "found no association between any
prenatal infection and ASD."
The takeaway
"An
important message is that even though we find an increased risk of ASD
after influenza and prolonged periods of fever during pregnancy, the
study is still speculative," lead study author Dr. Hjördis Osk
Atladottir said in an e-mail. "It is important to bear in mind that when
you look at the absolute numbers, we see that around 99% of women
reporting to have had influenza or fever during pregnancy do not have
children with ASD. We do not want pregnant women to worry. Our results
are truly explorative."
She and her co-authors strongly recommend further research in this area.
In
the meantime, Dr. Max Wiznitzer, a child neurologist at Rainbow Babies
& Children's Hospital in Cleveland, says that since this study
suggests the possibility of an association between influenza and autism,
it reinforces the recommendation that pregnant women should get a flu
shot, as recommended by the CDC.
