The Small-for-Gestational Age Infant

Abstract

After completing this article, readers should be able to: 1. Compare and contrast symmetric and asymmetric growth in small-for-gestational age (SGA) infants. 2. Describe common physical characteristics of the SGA infant. 3. Describe common problems encountered in SGA infants and their management. 4. Characterize postnatal growth and neurodevelopmental outcomes of SGA infants. More than 50 years ago, pediatricians and early “neonatologists” observed that newborns who had birthweights that were statistically less than the 10th percentile or 2 standard deviations below the mean weight for their gestational age experienced unique medical problems. These infants, termed small for gestational age (SGA), had more frequent problems with perinatal depression (“asphyxia”), hypothermia, hypoglycemia, polycythemia, long-term deficits in growth, and neurodevelopmental handicaps and higher rates of fetal and neonatal mortality (Fig. 1⇓ ). Despite improvements in perinatal diagnosis and treatment, SGA infants are still born regularly (more frequently in underdeveloped countries, but also in the United States and other developed areas), and their perinatal morbidity and mortality rates continue to exceed those of normal fetuses and infants. Figure 1. Morbidities specific to SGA infants. Adapted from Lubchenco LO. The High Risk Infant . Vol. XIV. In: Schaffer AJ, Markowitz M, eds. Major Problems in Clinical Pediatrics . Philadelphia, Pa: WB Saunders; 1976. As the specific morbidities associated with SGA infants were recognized, relatively standardized approaches to their evaluation and clinical management were established. However, there always have been conflicting data in the literature regarding differences between SGA and appropriate-for-gestational age (AGA) infants in areas such as long-term outcome, nutrient metabolism, and growth potential. Recent literature suggest that adults who experienced severe growth restriction in utero have a significantly increased incidence of hypertension, insulin resistance, and type 2 diabetes. Additionally, new evidence suggests that untoward metabolic events in utero that produce fetal growth restriction also may produce lifelong alterations in growth …