Smoking
during pregnancy can be harmful for both mother and baby. Now, a new study
provides further evidence that maternal smoking is a risk factor for cerebral
palsy in offspring, and it has shed light on the mechanisms behind this
association.
According to the Centers for Disease Control
and Prevention (CDC), around 55 percent of mothers who smoke prior to
becoming pregnant quit the habit during pregnancy.
However, around 10 percent of expectant
mothers in the United States still smoke in the final 3 months of pregnancy.
Smoking during pregnancy is a risk factor for
numerous health problems among offspring, including premature birth, birth
defects - such as cleft lip, or cleft palate - and sudden infant death
syndrome.
Previous research has also linked maternal smoking
with a greater likelihood of cerebral palsy in children, but the processes underlying this
association have been unclear.
The new study - led by Dr. Hui Chen, of the
University of Technology Sydney in Australia - teaches us more about the
subject.
Smoke exposure and cerebral
palsy
Cerebral palsy is a movement and balance
disorder that is estimated to affect around 1 in 323 children in the U.S.
The condition is caused by damage to the
developing brain. This may occur before birth, during birth, within 1 month of
birth, or in a child's early years.
One cause of cerebral palsy is the brain being
starved of oxygen-rich blood in the womb, a process known as hypoxia-ischemic
injury (HII).
The new research - recently published in the
journal Frontiers in Molecular Neuroscience - reveals how exposure to
cigarette smoke in the womb can worsen responses to HII, causing cell death in
brain regions associated with motor skills and memory, which are regions
implicated in cerebral palsy.
The
researchers came to their findings by studying mice born to mothers that had
been exposed to cigarette smoke before and during pregnancy.
The team tested the motor skills of the mouse pups and found that they
demonstrated movement problems similar to those that arise in cerebral palsy.
"We
found that pups from smoking mothers are more clumsy at adolescent age, have
less strength in their limbs, are more anxious, and have poor memory function
which many affect their learning ability," says Dr. Chen.
'Stop smoking long before pregnancy'
On
further investigation, the team found that the movement problems seen in the
mouse pups were due to an increase in oxidative stress, which is
the imbalance between antioxidants and harmful molecules called free radicals.
Dr. Chen explains that HII caused by cigarette smoke exposure prevents
mitochondria - which are the "powerhouses" of cells - from producing
sufficient amounts of antioxidants, allowing free radicals to accumulate and
cause damage to brain cells.
The
researchers believe their that findings provide yet another reason for
expectant mothers to stop smoking, and they suggest that the earlier smoking is
ceased, the better.
"What
we have observed so far," says Dr. Chen, "is that in order to avoid
harm to their baby, mothers need to give up smoking several months or even
years before their pregnancy, as smoking will affect the quality of their eggs
before they are even fertilized."
The
team now plans to assess whether or not antioxidants could be used to reduce
the harms of maternal smoke exposure among offspring; a previous study they
conducted indicated that an antioxidant called L-carnitine improved kidney and
respiratory function in mouse pups born to mothers exposed to cigarette smoke
in pregnancy.
"The
next step will be to use such a treatment to improve functional outcomes in
pups from the smoking mothers," says Dr. Chen.
"However, the message for the public is if you want a healthy baby, you
need toquit smoking long before you plan for the pregnancy.
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