While only 6% of the 456 women studied did smoke while pregnant, the babies born to those 30 women had systolic blood pressure that was 5.4 points higher on average than that of babies born to nonsmokers.

Systolic blood pressure is the higher of the two numbers used in a reading, measuring pressure when the heart is fully contracted. The researchers, at the University Medical Center, Utrecht, found no relationship between maternal smoking and diastolic blood pressure, the bottom reading.

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

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.

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.

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.