Most babies are born after 40 weeks of pregnancy. However, a significant number of children come into the world early.
There are many reasons why babies are born 'pre-term'. In developing countries, poor maternal care, poor nutrition for mothers, infections and disease can contribute to preterm birth. But some children in the industrialized world are also born early - and the numbers of preterm births are slowly rising. The reason for the increase is unclear.
Duke University obstetrics professor Geeta Swamy was interested in the long-term effects of being born prematurely. She says, "We don't know a lot about what happens to those
children [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 a million children born in Norway. She collected information about when they were born, what kinds of health problems they had and when they died.
Swamy focused on preterm children born before 37 weeks gestation, and also on children born before 28 weeks gestation? that's considered extremely preterm. 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. And that's particularly true for those girls who were born extremely preterm. For boys who were born extremely preterm, 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 mortality, up to about age 13.
Swamy says she also found long-term effects of being born early. Preterm 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. Among those women who were born extremely preterm, say, before 28 weeks, only 25% of those women actually went on to reproduce or have a child? We saw similar implications for men who are born preterm and term. For those who were born at term, about 50% of them went on to reproduce, compared to only about 14% of men who were born extremely preterm.
Swamy says scientists don't know for sure why prematurity confers such risk over the lifetime, and other studies are looking for those answers.
Her research is published in the Journal of the American Medical Association.