It is easy to quit smoking -- anyone can do it, for a brief time but not taking it up again -- that is the part that has proven so difficult for most people, especially those who have been exposed to nicotine before birth.

Researches have suggested that at pregnant women should quit smoking to avoid exposing their unborn children to nicotine, and that they should do so without the use of nicotine products such as patches or gums that also present a risk to the baby.

Smoking during pregnancy can harm the baby in ways that extend far beyond preterm delivery or low birth weight. It may cause changes in the brain development of the baby that can last a lifetime.The researchers studied two groups of rats: those that had been exposed to nicotine prenatally and those that had not. Initially, both groups of rats consumed nicotine at the same rates -- about ten hits per session. After four weeks, the researchers forced the rats to go "cold turkey" for a week, during which they had no access to nicotine. Once the scientists restored access to nicotine again, they witnessed a dramatic difference in the rates at which the two groups resumed the habit. The rats that had been exposed prenatally took nearly double the nicotine hits compared with those that had not.

While the rates of smoking in the United States are declining, approximately a quarter of Americans have mothers who smoked during pregnancy. Previous studies have shown these individuals have a higher chance of sudden infant death syndrome, attention deficit-hyperactivity disorder, obesity and even of becoming a lifelong smoker themselves.