small for gestational age (SGA) infant, a newborn whose weight and size at birth fall below the tenth percentile of appropriate for gestational age infants, whether delivered at term or earlier or later than term. Factors associated with smallness or retardation of intrauterine growth other than genetic influences include any disorder causing short stature, such as dwarfism; malnutrition caused by placental insufficiency; and certain infectious agents, including cytomegalovirus, rubella virus, and Toxoplasma gondii. Other factors associated with the smallness of an SGA infant include cigarette smoking by the mother during pregnancy, her addiction to alcohol or heroin, and her having received methadone treatment. Asphyxia may be a significant risk for the SGA infant during labor and delivery if the condition is the result of placental insufficiency. Such an infant has a low Apgar score, becomes acidotic in labor and at birth, and is likely to experience hypoglycemia within the first hours or days of life. Given adequate nutrition and caloric intake, some SGA infants show phenomenal catch-up growth. Also called small for dates (SFD) infant. Compare appropriate for gestational age (AGA) infant, large for gestational age (LGA) infant. See also dysmaturity.
