Women who take the epilepsy drug valproate during pregnancy
are three times more likely to have a child with an autism spectrum disorder,
suggests new research based on close to 700 000 babies born in Denmark.
Previous studies have found more birth defects and lower
intelligence among children of mothers who took valproate, but the new work
represents the "strongest evidence to date" of a link between the
drug and autism, according to an editorial published with the study.
The results don't prove the generic drug, also sold as
valproic acid, causes autism. But researchers were able to account for a number
of underlying factors - such as the age and health of the mothers and the
babies' fathers - that make the study more convincing, Christopher Stodgell
"This finding isn't necessarily a brand new finding,
but it's an important finding in that (researchers studied) really a much
larger population, and they also looked at some other underlying drivers,"
said Stodgell, who studies the origins of autism at the University of Rochester
Medical Center but wasn't involved in the new research. Women "need to be
very diligent about what the effects are if they're taking valproic acid,"
One in 88 is autistic
About one in 88 children has an autism spectrum disorder, or
ASD, according to the US Centers for Disease Control and Prevention. Those
conditions range from autism itself to less disabling ones such as Asperger's
syndrome. For the new study, researchers tracked 656 000 kids born in Denmark
between 1996 and 2006.
Using a large prescription drug database, they found that
just under 6 600 of the mothers of those children had epilepsy and 508 women
took valproate while pregnant. By 2010, 4.4% of the kids whose mothers had
taken valproate during pregnancy were diagnosed with any ASD, including 2.5%
In contrast, 1.5% of
all babies in the study had an ASD and 0.5%had autism, the study team reported
in the Journal of the American Medical Association. Mothers' underlying
epilepsy didn't fully explain the link, according to Jakob Christensen from
Aarhus University and his colleagues.
In addition, autism
rates were higher among children of women who used valproate during pregnancy
than those who had previously used the drug but stopped before conceiving.
Considering the risks
"Valproate is an effective drug, but it appears that it
is being prescribed for women of childbearing potential at a rate that does not
fully consider the ratio of benefits to risks," wrote Dr Kimford Meador
and David Loring from Emory University in Atlanta, in a linked editorial.
Valproate could affect maturation of a fetus's brain, Christensen suggested,
including the signal-sending neurotransmitters.
Women who may become pregnant "certainly should discuss
with their doctor if there are alternative treatments that would be
reasonable," he told Reuters Health. For those with certain syndromes or
generalized epilepsy, there aren't necessarily other good options. Stopping
valproate in that case isn't a good idea, Christensen said."It's also a
risk if you have seizures, both for the mother and the unborn child. (Stopping
medication) is not a thing that you take lightly," he said."Even
those that are exposed to this drug, there's still a good chance - more than a
95% chance - that their child will never develop signs of autism.
"The study didn't take into account whether women drank
during pregnancy, or if they took folic acid - which has been tied to a lower
risk of some birth defects. Christensen said there are steps pregnant women on
valproate can take to lower any risks to their baby, such as using the lowest
possible dose and dividing it up during the day.