Children of mothers who smoked during pregnancy had more damage to their arteries in young adulthood than offspring of non-smokers and the association was even stronger if both parents smoked, researchers reported in Arteriosclerosis, Thrombosis and Vascular Biology: Journal of the American Heart Association.

Researchers from The Netherlands found children of mothers who smoked during pregnancy had linings of carotid arteries in the neck that were 13.4 micrometers thicker by young adulthood than offspring whose mothers didn't smoke. The association was present even after adjustment for known risk factors such as age, gender, body mass index and cholesterol levels.

Thickness of the inner lining of the carotid arteries in study participants was associated with one parent smoking in pregnancy, somewhat stronger with exclusive maternal smoking and strongest if both parents smoked, the researchers reported.

"To our knowledge, this is the first study to demonstrate that exposure to parental tobacco smoking may lead to permanent vascular damage in their children and might be initiated early in life," said C.S.P.M. Uiterwaal, M.D., Ph.D., senior author of the study and associate professor of clinical epidemiology at the Julius Center for Health Sciences and Primary Care, University Medical Center, Utrecht.

The study included 732 young adults, average age 28, born in the 1970's when smoking was more common. Twenty-nine percent of the mothers smoked during pregnancy and more than 60 percent of the fathers smoked.

Researchers obtained data on parental smoking through standardized questionnaires. Participants also gave a smoking history and had blood pressure, lipid profiles and body mass index taken. Participants also underwent ultrasound to measure their carotid artery intima-media thickness (CIMT).

Researchers found that offspring of mothers who smoked were lighter and shorter at birth, heavier in adolescence and more likely to be smokers in young adulthood. However, this did not hold true if the young adults were offspring of just smoking fathers.

Adjustments for the current smoking of mothers, fathers and young adult participants did not change the association between parental smoking in pregnancy and thicker arterial walls. Neither did adjusting for education or income change the association.

The interaction between the participants' current smoking behavior and maternal smoking during pregnancy could indicate that if the cardiovascular system is exposed to tobacco smoke during pregnancy, the vessels are more vulnerable to tobacco smoke later in life, researchers said.

"It is difficult to tell what the increased risk of cardiovascular disease is in these young adults since they are still young," Uiterwaal said. "The damage is still sub-clinical, but we know that increased thickness of the arterial walls is an increased risk for real disease in older adults."

Fortunately, while 30 percent of the women smoked during pregnancy in the 70's, today only about 10 percent smoke during pregnancy," he said. "But we need people to understand that they shouldn't smoke whatsoever, whether it is during or outside of pregnancy. The lesson is, 'Don't smoke.'"

Uiterwaal said further study is required to confirm whether smoke exposure causes the damage. He said the researchers plan another study of younger offspring to determine if the same vessel wall thickness occurs in 5-year-olds who are the children of smoking parents.

Smoking in the family can contribute to vascular wall damage and it might be a process that starts even before birth, Uiterwaal said. "If we can manage to get women to stop smoking during pregnancy, this may provide a substantial advantage in the fight against cardiovascular disease."

The Atherosclerosis Risk in Young Adults study was funded by The Netherlands Organization of Health Research and Development Council.

Co-authors are: Caroline C. Geerts, M.D.; Michiel L. Bots, M.D., Ph.D.; and Diederick E. Grobbee, M.D., Ph.D.