Weight for gestational age affects the mortality of late preterm infants.
BACKGROUND
Late preterm infant mortality is higher than that for term newborns. The association between weight for gestational age (WGA) category and late preterm mortality has not been well described.


OBJECTIVE
Our objectives for this research were as follows: (1) to compare neonatal and infant mortality rates of SGA, AGA, and LGA late preterm, early term, and term newborns; (2) to determine the relative risk of neonatal and infant death for each WGA category; and (3) to examine causes of neonatal and infant death.


METHODS
We reviewed linked birth and death certificate data for all infants from Utah born between 1999 and 2005 with a GA > or =34 weeks. We calculated neonatal and infant mortality rates for each GA/birth weight stratum and estimated mortality rate ratios using AGA term infants as the reference. International Classification of Diseases, Ninth Revision, codes were used to classify cause of death.


RESULTS
There were 343322 newborns with GA > or =34 weeks from 1999 to 2005. Late preterm SGA infants were approximately 44 times more likely than term AGA newborns to die in their first month and 22 times more likely to die in their first year. When infants dying from congenital conditions were excluded, the differences in mortality rate ratios persisted for SGA infants, especially those born in the late preterm period.


CONCLUSIONS
Being SGA substantially increases the already higher mortality of late preterm and early term newborns. This increased risk cannot be fully explained by an increased prevalence of lethal congenital conditions among SGA late preterm newborns. Clinicians caring for late preterm and early term newborns should be cognizant of their WGA category.
Pulver
Laurie S
LS
Department of Pediatrics, University of Utah, Salt Lake City, UT 84158, USA. laurie.pulver@hsc.utah.edu
Guest-Warnick
Ginger
G
Stoddard
Gregory J
GJ
Byington
Carrie L
CL
Young
Paul C
PC
D001724:Birth Weight; D002423:Cause of Death; D015331:Cohort Studies; D005260:Female; D005865:Gestational Age; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007235:Infant, Premature, Diseases / Q000401:mortality*; D007236:Infant, Small for Gestational Age; D008297:Male; D016017:Odds Ratio; D012189:Retrospective Studies; D015996:Survival Rate; D047929:Term Birth; D014589:Utah