Small for Gestational Age: The Differential Mortality When Detected versus Undetected Antenatally

Abstract

Background Antenatal detection of fetal growth restriction (FGR) prompts antepartum surveillance to reduce perinatal mortality, yet most cases of FGR are undetected.

Objective This study aims to compare rates of adverse neonatal outcomes when FGR is detected versus undetected.

Study Design Small-for-gestational-age (SGA) newborns (birth weight < 10% for gestational age) delivered at the Magee-Women's Hospital in Pittsburgh, PA from 2003 to 2010 were divided into three groups: those whom did not undergo third-trimester fetal growth ultrasound (SGA-no US), were appropriate for gestational age (AGA) by ultrasound (SGA-undetected), or were FGR by ultrasound (SGA-detected). We then compared rates of 5-minute Apgar < 4 and neonatal death (ND), with AGA newborns as the referent.

Results Out of 29,885 neonates, 2,475 (8.3%) were SGA. Out of the 826 (33%) SGA neonates who underwent growth ultrasound, 185 (22%) were considered FGR. In the SGA-no US group, the adjusted odds ratio (aOR) for Apgar < 4 was 2.84 (95% confidence interval (CI): 1.28–6.29) and 3.87 (95% CI: 2.09–7.18) for ND. The risk of Apgar < 4 (aOR: 3.10, 95% CI: 0.93–10.28) and ND (aOR: 2.16, 95% CI: 0.66–7.14) were not significantly elevated for SGA-undetected neonates, while SGA-detected neonates were most at risk, with an aOR of 18.20 (95% CI: 6.82–48.60) for Apgar < 4 and 18.24 (95% CI: 7.90–42.13) for ND.

Conclusion Fetal growth ultrasound effectively stratifies risk amongst SGA neonates.

Keywords

fetal growth restriction - fetal growth ultrasound - small for gestational age - neonatal mortality

Note

These findings were presented at the 35th Annual Meeting of the Society for Maternal Fetal Medicine; February 6, 2015; San Diego, CA.

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