SMOKING DURING PREGNANCY ALTERS NEW BORN STRESS HORMONES
Researchers from The
Miriam Hospital have studied the effects of smoking during pregnancy and its
impact on the stress response in newborn babies. Their research indicates that
newborns of mothers who smoke cigarettes during pregnancy show lower levels of stress
hormones, lowered stress response, and alterations in DNA for a gene that
regulates passage of stress hormones from mother to fetus. The study and its
findings have been published in the journal Psychoneuroendocrinology
Our results suggest
that these newborns may not be mounting adequate hormonal response to daily
stressors. Their stress systems may not be prepared for the stressors of daily
life," says lead researcher Laura Stroud, Ph.D., of the Centers for Behavioral
and Preventive Medicine at The Miriam Hospital. "This may be particularly
detrimental in babies born to mothers who lack resources and parenting skills
and whose babies may encounter more daily stressors."
National health
statistics show that despite the warnings and known health risks, approximately
one in 10 expectant moms in the United States continue to smoke during
pregnancy, with higher rates among young, poor, and underserved moms. Babies
born to smoking mothers are born smaller, are more likely to be premature, and
are at greater risk for medical complications. Smoking during pregnancy is also
associated with long-term behavioral and health problems in child and adult
offspring, including asthma, behavior and attention problems, and nicotine
addiction. However, biological mechanisms underlying short and long-term
effects of smoking during pregnancy on offspring are not well understood.
"One possibility
is alterations in stress hormones and epigenetic changes (chemical
modifications) in DNA" Stroud says. "We were interested in stress
hormones because alterations in stress hormones have been linked to both
smoking and behavior problems and because maternal stress hormones during
pregnancy exert potent long-term effects on offspring. In particular, we sought
to investigate effects of smoking during pregnancy on the newborn stress
hormone cortisol." Cortisol is part of the hypothalamic pituitary
adrenocortical system that works synergistically with the "fight
flight" stress system.
Stroud also
investigated the effects of smoking during pregnancy on DNA in the placenta,
the temporary organ joining the mother and fetus during pregnancy. Stroud was
interested in studying epigenetic changes, or chemical modifications that turn
genes on and off, in DNA for the glucocorticoid receptor gene that regulates
passage of cortisol from mother to fetus.
Stroud's study
included 100 mother-newborn pairs from a low-income, racially and ethnically
diverse sample. Smoking in the mothers was examined through interviews that
covered each day of pregnancy -- with mothers' reports confirmed by measuring
nicotine levels. After babies were born, placentas were collected and DNA was
analyzed for alterations in the glucocorticoid receptor. Newborns' cortisol
levels were measured during and after neurobehavioral exams (involving
behavioral responses to different stimuli, reflex testing, and observation)
conducted seven times over the first month of life.
Results showed that
infants exposed to smoking showed lowered cortisol levels at baseline and in
response to the neurobehavioral exam, a behavioral stressor. The lowered
cortisol responses were consistent across seven behavioral exams over the first
month of life. In addition, effects of smoking during pregnancy on infant
cortisol and stress response were explained by alterations in DNA for a gene
that regulates passage of cortisol from mother to fetus.
"Our results also
suggest that effects of smoking during pregnancy on infant stress response are
explained by changes in DNA," Stroud says. "Because these DNA changes
are epigenetic, there is a hopeful message that perhaps some of these changes
could be undone by environment or medications."
Stroud concludes,
"These alterations in stress hormones, stress response, and DNA may
explain links between moms' smoking during pregnancy and the risk for their
children to have behavior problems and nicotine addiction in later life. Our
results offer one more reason for mothers to quit smoking, and also highlight
the need for early intervention with babies born to mothers who smoke during
pregnancy and the mothers themselves."
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