Differences in Mortality between Late-Preterm and Term Singleton Infants in the United States, 1995–2002

Objective

To assess differences in mortality between late-preterm (34-36 weeks) and term (37-41 weeks) infants.

Study design

We used US period-linked birth/infant death files for 1995 to 2002 to compare overall and cause-specific early-neonatal, late-neonatal, postneonatal, and infant mortality rates between singleton late-preterm infants and term infants.

Results

Significant declines in mortality rates were observed for late-preterm and term infants at all age-at-death categories, except the late-neonatal period. Despite the decline in rates since 1995, infant mortality rates in 2002 were 3 times higher in late-preterm infants than term infants (7.9 versus 2.4 deaths per 1000 live births); early, late, and postneonatal rates were 6, 3, and 2 times higher, respectively. During infancy, late-preterm infants were approximately 4 times more likely than term infants to die of congenital malformations (leading cause), newborn bacterial sepsis, and complications of placenta, cord, and membranes. Early-neonatal cause-specific mortality rates were most disparate, especially deaths caused by atelectasis, maternal complications of pregnancy, and congenital malformations.

Conclusions

Late-preterm infants have higher mortality rates than term infants throughout infancy. Our findings may be used to guide obstetrical and pediatric decision-making.

Abbreviations: ICD, International Classification of Diseases, LMP, Last normal menstrual period, NCHS, National Center for Health Statistics, SIDS, Sudden Infant Death Syndrome