Small for gestational age at term: How small is too small?

Abstract

YVONNE CHENG, JUDITH CHUNG, ALLISON BRYANT, AARON CAUGHEY, University of California, San Francisco, Department of Obstetrics, Gynecology and Reproductive Sciences, San Francisco, California, University of California, Irvine, Department of Obstetrics & Gynecology, Orange, California OBJECTIVE: To examine perinatal outcomes of term neonates with birthweight less than tenth percentile by gestational age. STUDY DESIGN: This is a retrospective cohort study of singleton, cephalic term neonates. Birthweight was stratified into !3rd, 3-4th, 5-9th, and 10-90th percentile subgroups by gestational age at delivery. Rates of cesarean delivery for fetal intolerance of labor (CD-FIOL) and neonatal outcomes were examined using chi-square test and multivariate logistic regression analyses controlling for potential confounders. RESULTS: There were 14,974 births meeting study criteria. In univariate analyses, there were differences between the four groups (Table). Compared to the 10-90th percentile subgroup, neonates with birthweight !3rd percentile were more likely have cesarean delivery for FIOL (OR=2.49; 95% CI[1.454.26]), 5-minute Apgar !7 (OR=2.21; [1.39-3.53]), umbilical artery cord pH!7.0 (OR=3.63; [1.51-8.71]), jaundice (OR=2.04; [1.50-2.79]), and be admitted to the intensive care nursery (ICN, OR=4.30; [3.15-5.87]. These outcomes were not statistically significant for neonates with birthweight in the 3-4th and 5-9th percentiles when controlling for confounders. CONCLUSION: Although small, neonates with birthweight greater than the 3rd percentile did not experience higher risk of neonatal morbidity compared to their average for gestational age counterparts. However, neonates with birthweight less than the third percentile by gestational age had higher risk of neonatal morbidity. This information may be useful in counseling and managing women with pregnancies suspicious for small for gestational age.