SGA subtypes and mortality risk among singleton births

Abstract

Objectives: To determine whether early mortality (first year of life) risks among small for gestational age (SGA) neonates were similar regardless of SGA subtype based on three chronological classifications (term, preterm and post-term).

Study design: Retrospective cohort study on all singleton live births in the United States from 1995 to 1999 inclusive. Adjusted risk estimates were computed from logistic regression models using non-SGA infants as the referent.

Results: When SGA infants were compared as a homogeneous entity to non-SGA infants, the risks for infant, neonatal and post-neonatal mortality were significantly greater in SGA infants [AOR (adjusted odds ratio)=3.0, 95% CI (confidence interval)=2.9-3.0 for infant mortality; AOR=3.2, 95% CI=3.1-3.2 for neonatal mortality; and AOR=2.6, 95% CI=2.6-2.7 for post-neonatal mortality]. However, heterogeneity existed in terms of mortality risk thresholds across SGA babies. The most remarkable risk magnitude was observed among preterm SGA infants [infant mortality AOR=13.8, 95% CI=13.6-14.1; neonatal death AOR=17.4, 95% CI=17.0-17.7; and post-neonatal death AOR=7.4, 95% CI=7.1-7.6]. The adjusted odds ratio for term and post-term SGA infants were comparable regardless of the period during infancy, and were much less than those observed for preterm SGA infants.

Conclusions: SGA is a heterogeneous disease in terms of prognosis for survival. Preterm SGA infants bear an extremely high risk for mortality during infancy, and counseling of affected parents should reflect this risk divergence.