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Preterm birth is associated with an increased risk of mortality for decades
Last reviewed: 02.07.2025
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Preterm birth is associated with an increased risk of death from birth through the third and fourth decades of life, according to a new study by researchers from Wake Forest University School of Medicine and SickKids Hospital in Toronto.
The study was published in JAMA Network Open.
Approximately 10% of all births worldwide are classified as preterm, meaning the baby is born before the 37th week of gestation. Preterm birth is the leading cause of infant mortality and the second leading cause of death among children under 5 years of age worldwide.
"Understanding the long-term consequences of preterm birth can help us develop prevention strategies and identify approaches to improve the health of people born preterm," said Asma M. Ahmed, MD, PhD, associate professor of epidemiology and prevention at Wake Forest University School of Medicine, a former postdoctoral fellow at SickKids Hospital, and lead author of the study.
Ahmed explained that while most people born prematurely survive into adulthood, there is growing evidence that there is an increased risk of death throughout life.
"We wanted to find out whether people born prematurely have a higher risk of both short-term and long-term mortality compared to those born at term," she added.
First population-based study in North America
In the first population-based study of preterm birth in North America, Ahmed and her team analyzed a cohort of nearly 5 million live births in Canada, of which 6.9% were preterm. Participants were born between 1983 and 1996 and followed until 2019, providing a follow-up period of 23 to 36 years.
Preterm births were divided into subcategories by gestational age: 24–27 weeks, 28–31 weeks, 32–33 weeks, and 34–36 weeks. These groups were compared with those born at term, 37–41 weeks.
Key findings of the study
The researchers found that preterm birth was associated with an increased risk of death across all age groups up to age 36, with the greatest risks seen in infancy (0-11 months) and early childhood (1-5 years).
"We also found that the risk of mortality was higher with lower gestational age at birth, with the highest risk occurring in babies born before 28 weeks," Ahmed said.
The study also found increased mortality risks associated with various causes, such as diseases of the respiratory, cardiovascular and digestive systems, nervous and endocrine systems, infectious diseases, cancer and congenital malformations.
"These results indicate that preterm birth should be considered a significant risk factor for mortality," Ahmed said. "The risk persists into the third and fourth decades of life. While clinical care in the neonatal period is critical, long-term follow-up and monitoring of the health of people born preterm is also essential."
Future research directions
Ahmed added that more research is needed in other populations, particularly in low- and middle-income countries where preterm birth rates are highest. She also stressed the importance of studying the factors that underlie the increased risk of death after preterm birth.