Babies who are too little when they're born tend to have all kinds of health problems during infancy. But evidence is showing that health problems persist even as these children age - all as a result of being born underweight.

Now research finds that babies born small are likely to grow up to have high blood pressure once they're adults.

Researchers in the state of Louisiana have been studying the health of about 15,000 people in the semi-rural town of Bogalusa for the past 35 years. Dr. Gerald Berenson has been one of the primary investigators for the study since it began.

Berenson has noted that in this multi-racial group of people, the average weight of black babies is smaller than those of whites. Berenson found that was true no matter the health or wealth of their mothers.

"They are? lighter by a few hundred grams in the blacks compared to whites," Berenson says. "So right off, there is a difference in birth weights, and males tend to have heavier birth weights than do females."

Low birth weight is defined as being below 2,500 grams at birth.  Berenson says after he looked at the data on 8,000 black and white babies who are now in their 30s and 40s, he found the adults born small had higher blood pressure readings, even considering the typical increase that comes with age.

"We see a greater effect as individuals get older," Berenson says. "It may be because they begin to get higher blood pressure as people get older. And the effect of the low birth weight may become exaggerated at that point."

Berenson says he's not sure why this happens. He cites evidence from human and animal studies that points to the importance of the prenatal environment on life-long health.

"We know that smoking, for example, affects the blood vessels in the placenta. We know that alcohol is bad," Berenson says. "General nutrition, particularly in the early trimester, is very critical. That development in the early period of gestation is? is very important. So a baby in utero, early in development, is showing the effects of the environment."

Berenson says findings like these reinforce the message that taking care of health before and during pregnancy is key for the development of healthy children.  He's continuing to collect data from the people in Bogalusa and to analyze the effects of childhood health on long-term outcomes.

Berenson recently presented his data at a meeting of the American Society for Hypertension.