How A Pregnant Woman's Choices Could Shape A Child's Health
by JON HAMILTON
September 23, 2013 3:37 AM
4 min 38 sec
Does a glass or two of wine
during pregnancy really increase the child's health risks? Epigenetics may help
scientists figure that out.
Katherine Streeter for NPR
Pregnant women hear a lot about
things they should avoid: alcohol, tobacco, chemical exposures, stress. All of
those have the potential to affect a developing fetus. And now scientists are
beginning to understand why.
One important factor, they say,
is something called epigenetics, which involves the mechanisms that turn
individual genes on and off in a cell.
There's growing evidence that
epigenetics is critical in determining a child's risk of developing problems
ranging from autism to diabetes, says Dani Fallin,
who studies the genetics of mental disorders at Johns Hopkins Bloomberg School
of Public Health.
Epigenetic control of genes is
part of what allows a tiny cluster of identical cells in the womb to grow into
a fully formed baby. By switching certain genes on and off, some cells become
heart cells while others become brain cells.
It's a delicate process that can
be disrupted by exposure to certain chemicals or hormones, says Susan Kay Murphy, an
associate professor of obstetrics and gynecology at Duke University School of
Medicine. And the first week or so after conception appears to be "a
particularly vulnerable time where environmental influences can directly affect
an epigenetic outcome," she says.
Murphy's interest in epigenetics
is personal as well as professional. She entered the field in the 1990s after
her young son died from a rare form of liver cancer that has been linked to
epigenetic changes. She also has a son with autism and a daughter with ADHD.
Much of what's known about the
epigenetics of pregnancy comes from experiments with mice, specifically a group
of genetically identical agouti mice.
When these mice are exposed to certain chemicals or put on a special diet
during pregnancy, it switches on the agouti gene in their offspring. That
causes the pups to produce a lot of agouti protein, which turns their fur a
striking yellow.
The agouti protein also prevents
these mice from feeling full, no matter how much they eat, Murphy says.
"So they become very obese and are predisposed to developing diabetes and
cancer," she says
To learn whether something like
that can happen in people, Murphy has been doing a studythat looks at how a mother's
environmental exposures and nutrition during pregnancy may be causing
epigenetic changes in babies.
The study has already produced
some interesting results involving folic acid, a vitamin many pregnant women
take to reduce the risk of problems like spina bifida. "At the recommended
levels, it's beneficial," Murphy says. "At very high levels you
actually lose that benefit."
But the results of epigenetic
changes don't necessarily appear at birth or even during childhood. That's
because things that affect development very early in life can show up decades
later, she says.
"If you think of development
as a ball rolling down a creviced hill, there are many different paths that
ball can take," Fallin says. "And epigenetic mechanisms may help
shape that path."
So what happens in the womb may
cause epigenetic changes that contribute to schizophrenia or diabetes decades
later, she says.
Fallin is particularly interested
in early developmental paths that can lead to autism. So she did a study looking at
epigenetic information in the brain cells of children with autism and
neurotypical kids.
"At specific places, we see
differences in the brains from the autistic children," she says.
"That's important because those particular genes may give us a clue about
what's being turned on and off differently in autistic children."
A complete epigenetic explanation
of autism or any other disease is a long way off, Fallin says. But in the
meantime, epigenetic studies may help get the attention of pregnant women who
would otherwise ignore recommendations about diet and behavior.
"If you see there is a
detectable biological change because of exposure to drinking or because of
exposure to smoking, that as a pregnant mom would convince me that, oh, it
matters," she says.
Fallin has two children, and she
hopes that epigenetic evidence will eventually make it clearer how much
exposure is a problem during pregnancy. She says that might finally settle the
question of whether it's OK for a pregnant woman to have a glass of wine with
dinner.
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