Babies who weigh six pounds or less at birth or more than 9.4 pounds are far more likely to die earlier as an adult than babies of average weight, which is 7.1 to 8.3 pounds, according to new research from the Centre for Health and Society in Copenhagen, Denmark.

Reuters Health reports that previous research has linked low birth weights to an increased risk later in life of heart disease and diabetes, while heavy babies grow up with a heightened risk of obesity and cancer. But previous studies trying to show a link between birth weight and mortality risk have had mixed results, especially since no single study has examined more than 29 consecutive birth years. Until now.

The Danish study is the largest to date with data collected on 216,464 men and women born over a 44-year span from 1936 to 1967. Led by Dr. Jennifer Baker, the team compared birth weight with risk of death from any cause from age 25 to 68. Younger people were followed through 2004. "More infants than ever before are being born with these high birth weights," Baker told Reuters Health. "Further research is really needed to determine what may happen to these children when they grow up."

What did they find? Babies of both genders who were 4.4 to 6.0 pounds at birth had a 17 percent greater risk of death during the study follow-up period, compared with those whose birth weights were between 7.1 and 8.3 pounds. Heavier babies--those with birth weights from 9.4 to 12.1 pounds--had a 7 percent increased chance of dying.

What are the leading causes of death? Deaths from cardiovascular disease followed a similar "U-shaped" pattern, reports Reuters. The risk of dying from cancer was lowest for those with the lowest birth weight and increased steadily as the birth weight rose. Babies of both low and high birth weight tended to develop low blood sugar, while the smallest infants developed high blood sugar. "Sustained exposure to either state can permanently impair brain development," Baker said. "We speculate that this could lead to cognitive deficits and impairments in the regulation of body processes, which might contribute to the elevated risks of mortality observed at both ends of the birth weight spectrum."

The study was published in the journal Epidemiology.

--From the Editors at Netscape