The real concern is that, "one finds that blood pressure tracks over time, so someone with high pressure at a young age typically becomes hypertensive later in life," explained Daniel T. Lackland, professor of epidemiology at the Medical University of South Carolina, and a spokesman for the American Heart Association. He was not involved in the study.

Perhaps more significant than the blood pressure result was the finding that babies of smoking women in the study had significantly lower birth weights, were shorter and had a smaller chest circumference than babies of nonsmokers, Lackland said.

"One element that really stands out is this intrauterine growth retardation," Lackland said. "Smoking affects fetal life, so it essentially is affecting the baby for life."

The study, which is expected to be published in the September issue of Hypertension, did have some shortcomings, said Dr. Michael Katz, senior vice president for research and global programs at the March of Dimes Birth Defects Foundation. For example, it relied on questionnaires for information on the women's smoking habits, and they are not completely reliable, he said.

Still, the study does add support to the long-standing recommendation that no woman who is pregnant or might become pregnant should smoke, Katz said.

"One thing you don't have to look for is another argument against smoking," he said. "Every aspect of it is bad. It is one of the worst poisons we have."

But the increase in infant blood pressure could be significant if it persists, Katz said. "What is very important is how long this lasts," he said. "Is this a phenomenon that will wear itself out? It would require a long-term study to determine that."

The Dutch researchers said they plan to follow the children for at least four to five years to see if the increase in systolic blood pressure persists.

Even if the rise in blood pressure is found not to continue to later life, Katz said the study results "add an additional straw, and the camel's back is breaking," referring to the many damaging effects of maternal smoking on the fetus. It never hurts to have one more evidence of damage to present to women of childbearing age, he said.

"Who knows at what point in the various arguments the conviction that smoking in pregnancy is bad will prevail?" he asked. "Women who have trouble with their blood pressure might respond to this, too."

More information

More detailed information on the dangers of smoking during pregnancy is provided by the March of Dimes Birth Defects Foundation