Objectives: The purpose of this work was to determine the relative risk for mortality and the causes and ages of death for late-preterm newborns (gestational age of 34-36 weeks) compared with those born at term.
Methods: We reviewed data from birth and death certificates of infants born in Utah between 1999 and 2004. We calculated early neonatal (first week), neonatal (first 28 days), and infant (first year) mortality rates for each weekly estimated gestational age cohort from 34 to 42 weeks and, using 40 weeks as the reference, risk ratios for each cohort. Causes of death were grouped into 8 categories and compared for near term and term newborns. Crude mortality rates and risk ratios for death from all causes and for infants dying of all causes other than birth defects were measured.
Results: Birth defects were the single-most common cause of death for both term and late-preterm newborns. Mortality rates for late-preterm newborns remained significantly higher after excluding those who died of birth defects from the comparisons.
Conclusions: Compared with those born at term, late-preterm (near-term) newborns have significantly higher mortality rates. Each weekly increase in estimated gestational age is associated with a decreasing risk of death. Birth defects are the leading cause of death among late-preterm newborns but do not entirely account for their higher risk of death.