Smoking During Pregnancy Alters DNA and Stress Hormones in Newborns

Scientists have made a startling discovery when it comes to smoking during pregnancy. They found 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.

About one in 10 expectant mothers in the United States continue to smoke during pregnancy, with higher rates among the young and poor. Babies born to smoking mothers are usually born smaller, are more likely to be premature and are at greater risk of medical complications. That's why scientists decided to take a closer look at the biological mechanisms involved.

The researchers investigated effects of smoking during pregnancy of the newborn stress hormone cortisol. They also examined the effects of smoking during pregnancy on DNA in the placenta, the temporary organ joining the mother and fetus during pregnancy.

"Our results suggest that these newborns may not be mounting adequate hormonal responses to daily stressors," said Laura Stroud, the lead researcher, in a news release. "Their stress systems may not be prepared for the stressors of daily life. This may be particularly detrimental in babies born to mothers who lack resources and parenting skills and whose babies may encounter more daily stressors."

In fact, the scientists found 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. Not only that, but the scientists found that smoking during pregnancy caused alterations in DNA for a gene that regulates the passage of cortisol from mother to fetus.

"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 later in life," said Stroud. "Our results offer one more reason for mother to quit smoking, and also highlight the need for early intervention with babies born to mothers who smoke during pregnancy and the mothers themselves."

The findings are published in the journal Psychoneuroendocrinology.