Abstract
Objective The similarity in size among siblings has implications for neonatal death, but research
in this area is lacking in the United States. We examined the association between
small-for-gestational age (SGA), defined as a birthweight <10th percentile for gestational
age, and neonatal death, defined as death within the first 28 days of life, among
second births who had an elder sibling with SGA (“repeaters”) versus those whose elder
sibling did not have SGA (“nonrepeaters”).
Study Design We conducted a population-based retrospective cohort study including 179,436 women
who had their first two nonanomalous singleton live births in Missouri (1989–2005).
Logistic regression was used to evaluate the association between SGA and neonatal
death among second births, stratified by whether the elder sibling was SGA.
Results Out of 179,436 second births, 297 died in the neonatal period. There was a significant
interaction between birthweight-for-gestational age of first and second births in
relation to neonatal death (p = 0.001). Second births with SGA had increased odds of neonatal death by 2.15-fold
if they were “repeaters,” and 4.44-fold if they were “nonrepeaters,” as compared with
non-SGA second births.
Conclusion Our findings suggest that referencing sibling birthweight may be warranted when evaluating
infant size in relation to neonatal death.
Keywords
birthweight - Missouri - neonatal death - sibling data
