Most babies are born after 40 weeks of pregnancy. However, a significant number of children come into the world early, and, as Rose Hoban reports, they can face life-long problems.


There are many reasons why babies are born prematurely, or 'pre-term'. In developing countries, poor maternal care, poor nutrition for mothers, infections and disease all contribute to pre-term birth. But some children in the industrialized world are also born early - and the numbers of pre-term births there are slowly rising. The reason for this increase is unclear.


Duke University obstetrics professor Geeta Swamy is interested in the long-term effects of being born prematurely. She says scientists don't know a lot about what happens to children born early over the long term, "particularly as they grow up into adolescence and into adulthood. And what implications does this have on their long-term health?"


Swami was able to analyze the lifetime medical records of more than one million individuals born in Norway. She collected information about when they were born, what kinds of health problems they had during their lives and when they died.


Swamy focused on pre-term children born before 37 weeks gestation, and also on children born before 28 weeks gestation ? that's considered 'extremely' pre-term. She found children who were born early were also more likely to die early.


"For girls, the increased risk of mortality was about 10 times higher than those born at term," Swamy says. "And that's particularly true for those girls who were born extremely pre-term.  For boys who were born extremely pre-term, they had about a five-times increased risk of death during the early childhood age, up to about age 6, but they also had an increased risk of mortality up to about age 13."


Swamy says she also found the effects of being born early extended well into adulthood. Pre-term children ended up completing fewer years of education. And they were less likely to have children of their own.


"Among women who are born at term, roughly 70% of those women went on to reproduce or have a child," Swamy reports. "Among those women who were born extremely pre-term ? say, before 28 weeks ? only 25 percent of those women actually went on to reproduce or have a child."


Swamy found similar results for men. About 50 percent of men born at term went on to reproduce. Only about only about 14 percent of men who were born extremely pre-term had children of their own.


Swamy says scientists don't know for sure why prematurity confers such risk over a person's lifetime. Other studies are looking for those answers.

Her research is published in the Journal of the American Medical Association.