Background: Early-term birth (gestational age, 37–38 weeks) has been associated with increased infant mortality relative to later-term birth, but mortality beyond infancy has not been studied. We examined the association between early-term birth and mortality through young adulthood.
Methods: We conducted a national cohort study of 679,981 singleton births in Sweden in 1973–1979, followed up for all-cause and cause-specific mortality through 2008 (ages 29–36 years).
Results: There were 10,656 deaths in 21.5 million person-years of follow-up. Among those still alive at the beginning of each age range, early-term birth relative to those born at 39–42 weeks was associated with increased mortality in the neonatal period (0–27 days: adjusted hazard ratio = 2.18 [95% confidence interval = 1.89–2.51]), postneonatal period (28–364 days: 1.66 [1.44–1.92]), early childhood (1–5 years: 1.29 [1.10–1.51]), and young adulthood (18–36 years: 1.14 [1.05–1.24]), but not in late childhood/adolescence (6–17 years: 0.97 [0.84–1.12]). In young adulthood, early-term birth was strongly associated with death from congenital anomalies and endocrine disorders, especially diabetes (2.89 [1.54–5.43]).
Conclusions: In this large national cohort study, early-term birth was independently associated with increased mortality in infancy, early childhood, and young adulthood. Lowest short-term and long-term mortality was among those born at 39–42 weeks.
From the aDepartment of Medicine, Stanford University, Stanford, CA; bCenter for Primary Health Care Research, Lund University, Malmö, Sweden; and cStanford Prevention Research Center, Stanford University, Stanford, CA.
Submitted 5 April 2012; accepted 30 November 2012; posted 18 January 2013.
Supported by grants from the National Institute of Child Health and Human Development (1R01HD052848-01), the Swedish Research Council (2008-3110 and 2008-2638), the Swedish Council for Working Life and Social Research (2006-0386, 2007-1754, and 2007-1962), and ALF project grant, Lund, Sweden.
The authors report no conflict of interest.
Supplemental digital content is available through direct URL citations in the HTML and PDF versions of this article (www.epidem.com). This content is not peer-reviewed or copy-edited; it is the sole responsibility of the author.
Correspondence: Casey Crump, 211 Quarry Road, Suite 405, MC 5985, Palo Alto, CA 94304-1426. E-mail: email@example.com.