Survival, Hospitalization, and Acute-Care Costs of Very and Moderate Preterm Infants in the First 6 Years of Life: A Population-Based Study

Objectives: To investigate survival, hospitalization, and acute-care costs of very (28-31 weeks' gestation) and moderate preterm (32-33 weeks' gestation) infants in the first 6 years of life and compare outcomes with the more widely studied extremely preterm infants (24-27 weeks' gestation) and to full term (low risk) infants (39-40 weeks' gestation).

Study design: Birth data from all women residing in New South Wales, Australia, with gestational ages between 24-33 and 39-40 weeks in 2001-2011 were linked probabilistically to hospitalization and mortality data. Study outcomes were evaluated with the use of descriptive and multivariable analyses at birth (N = 559,532), discharge (N = 540,240), and at 1 (N = 487,447) and 6 years of age (N = 230,498).

Results: Mortality was greatest among extremely preterm infants (eg, 31.2% within 6 years) and decreased with increasing gestational age. Likewise, hospitalization within the first year of life increased with decreasing gestational age (aOR 5.5 [95% CI 4.7-6.4], 3.7 [3.4-4.0], and 2.6 [2.5-2.8] for birth at 24-27, 28-31, and 32-33 weeks' gestation, relative to 39-40 weeks' gestation). Hospitalization remained significantly increased with preterm birth at each year of age up to 6 years (aORs 1.3-1.6 at 6 years). Cumulative costs were significantly greater with preterm birth within the first year of life, and also between 1 and 6 years of age.

Conclusions: The risks of adverse health outcomes were significantly greater in very and moderately preterm infants relative to full term infants but lower than extremely preterm infants. Crucially, preterm birth was associated with prolonged increased odds of hospitalization (up to age 6 years), contributing to greater resource use.