Information gained from ultrasound is the diagnostic standard used to identify intrauterine growth restriction. Birth weight below the population 10th percentile, corrected for gestational age, is the most widely used definition of SGA.

Neonatal growth restriction is recognized as a syndrome that includes small size and specific metabolic abnormalities. These abnormalities include hypoglycemia (low blood sugar level), hypothermia (low body temperature), and polycythemia (increased level of red blood cells).