THURSDAY, Nov. 20 (HealthDay News) -- Damage to the arteries of children of smokers can be detected in the early decades of their lives, a new Dutch study finds.

"Smoking in families is harmful for children, including their cardiovascular system, as was found in many other studies," said research leader Dr. Cuno S.P.M. Uiterwaal, an associate professor of clinical epidemiology at the University Medical Center in Utrecht. "This study adds that tobacco smoke exposure may have such effects already in very early life."

Uiterwaal and his colleagues reported the finding in the December issue of Arteriosclerosis, Thrombosis and Vascular Biology that they used ultrasound to measure the thickness of the walls of carotid arteries, the major blood vessels to the brain, in 732 young adults, average age 28. Records showed that 29 percent of the mothers and more than 60 percent of the fathers smoked during the pregnancies.

The inner lining of the carotid arteries was thicker for the young adults who had both parents smoking during pregnancy, a sign of potential danger in the years ahead. The thickening was strongest for maternal smoking.

"We believe that our findings with regard to fetal exposure may serve as a first signal which will have to be confirmed by other research in this area," Uiterwaal said.

It has long been known that "exposure to tobacco smoke of pregnant women is bad for many reasons, such as low birth weight and increased risk for childhood respiratory disease," he said. "Our study now adds that it may also already harm the cardiovascular system of the unborn child."

The study does need confirmation, Uiterwaal said. "We are indeed trying to do a similar study in healthy young children, 5-year-olds, as that would eliminate many of the possibly confounding influences in later childhood," he said. "We are currently measuring arterial wall linings of these children of whom we know the gestational history."

A weakness of the current study is that it relied on the memories of participants about smoking histories, said Dr. Michael Katz, senior vice president for research and global programs at the March of Dimes Foundation.

And yet, Katz said, "the claim they make is probably valid, because it jibes with many previous studies showing the harmful effects of smoking during pregnancy, by anyone in the household."

"Any smoke in the environment is bad," Katz said. He cited a previous study that showed an increased risk of cleft palate among children of smokers, even if the mothers themselves did not smoke. "It's not by any mysterious way, just by inhaling," Katz said. "That is why smoke-free environments are desirable."

There was one pleasant surprise in doing a study of smoking during pregnancy in the Netherlands, Uiterwaal said. "The smoking rate of mothers in pregnancy of 29 percent in the early 1970s that we found in the present study has dropped to some 4 to 5 percent to date in the Netherlands," he said. "A very fortunate drop from a public health perspective, but it will make this issue more difficult to study at present."

Current estimates are that about 10 percent of American women smoke during pregnancy.

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