People who were exceptionally lightweight newborns may be at increased risk for type 2 diabetes and cardiovascular disease later in life, say researchers at the National Public Health Institute in Helsinki, Finland.

The researchers found that young adults who had a very low birth weight (VLBW) were more likely to show signs of impaired glucose regulation. They defined VLBW as being less than approximately 3 pounds, 5 ounces.

Fortunately, researchers say, knowing about low neonatal weight and disease risks upfront means people can improve their chances of avoiding type 2 diabetes later in life.

“We need to identify those that are small for gestational age and monitor them particularly carefully,” says Robert Rapaport, MD, director of the Division of Pediatric Endocrinology & Diabetes at the Mount Sinai School of Medicine, commenting on the study findings.

Researchers followed 163 VLBW young adults 18 to 27 years old and 169 peers who were born at term and weighed at least 5 pounds, 8 ounces. The VLBW subjects were almost 20 percent higher on the insulin-resistance index. They also showed an almost 10-percent increase in two-hour glucose concentration, as determined by an oral glucose tolerance test; a more than 15- percent increase in fasting insulin concentration; and a 40-percent increase in two-hour insulin concentration compared with non-VLBW subjects.

Why might VLBW hurt glucose regulation later on? Study authors said that the third trimester of pregnancy may be when key glucose-metabolism programming takes place in the fetus. And babies born very early, who are often small as well, miss out on some or all of that important stage of intrauterine development. Previous studies have shown that even when born at term, low-birth-weight babies are at risk for insulin sensitivity later in life.

This new study, published in the May 17, 2007, New England Journal of Medicine, joins a host of others that indicate potential consequences of VLBW, says Rapaport. Aside from insulin resistance and onset of type 2 diabetes, other risks include problems with cognitive ability, studies indicate.

Among the many possible contributors to VLBW are poor nutrition, smoking, and drug use during pregnancy. Placental abnormalities and fetal metabolism errors can also contribute to low birth weight.

To prevent VLBW, Rapaport advises ensuring that women are well nourished and have their blood glucose checked during pregnancy. He also recommends watching children born VLBW to make sure they catch up on growth. “We need to have children being monitored by pediatricians, with growth curves plotting weight and length [and BMI],” he says.