Preterm birth is associated with an increased risk of mortality in adulthood, research shows

Being born prematurely is associated with an increased risk of death from birth through the third and fourth decades of life, according to a new study from researchers at Wake Forest University School of Medicine and the Hospital for Sick Children (SickKids) in Toronto.

The study appears online today in JAMA network opened.

About 10% of all births worldwide are classified as preterm, which happens when a baby is born before 37 weeks’ gestation. Worldwide, premature birth is the leading cause of infant mortality and the second leading cause of death for children under the age of five.

“Understanding the long-term effects of preterm birth can help us develop preventive strategies and identify interventions to improve the health of people born prematurely,” said Asma M. Ahmed, M.D., Ph.D., assistant professor of epidemiology and prevention at Wake Forest University School of Medicine, former postdoctoral researcher at SickKids, and lead author of the study.

Ahmed said that while the majority of people born prematurely survive into adulthood, mounting evidence highlights an increased risk of death throughout life.

“We wanted to know whether people born prematurely have a higher risk of short- and long-term mortality compared to people born full-term,” Ahmed said.

In the first known population-based study of preterm birth in North America, Ahmed and his team analyzed a cohort of nearly 5 million live births in Canada, of which 6.9% were born preterm. Participants were born between 1983 and 1996 and were followed through 2019, yielding a follow-up period ranging from 23 to 36 years.

The preterm births were divided into subcategories of gestational age: 24–27 weeks, 28–31 weeks, 32–33 weeks, and 34–36 weeks, and compared with the full-term births, 37–41 weeks.

The researchers found that preterm birth is associated with an increased risk of death in all age groups up to age 36, with the highest risks occurring from birth to infancy, 0-11 months, and early childhood, 1-5 years.

“We also found that the risk of mortality is higher at lower gestational age at birth, with those born before 28 weeks at greatest risk,” Ahmed said.

The study also identified increased risks of mortality associated with various causes, such as respiratory, circulatory and digestive system diseases; nervous system, endocrine and infectious diseases; cancers; and congenital abnormalities.

“These findings suggest that preterm birth should be recognized as a significant risk factor for mortality,” Ahmed said. “The risk persists into the third and fourth decades of life. Although clinical care during the neonatal period is critical, long-term follow-up care and monitoring for premature people is critical to help limit the risks.”

Ahmed said additional research is needed in other populations, especially in low- and middle-income countries where preterm birth rates are the highest. She also emphasized the importance of research that identifies underlying factors that contribute to the increased mortality risk after preterm birth.