Small for gestational age infants are defined as having a birth weight more than 2SD below the mean or less than the 10th percentile of a population specific weight versus gestational age plot.
Infants whose weight is greater than the 10th percentile but who are thin relative to their length and head circumference are at similar risk of neonatal complications as SGA infants. They should be considered "relatively" SGA (Clifford syndrome).
The weight/length ratio (or the Ponderal Index = [weight (g)]/[length (cm)]3 ) is less than normal for such infants. However, unless great care is taken with the measurement of length the calculated index can be misleading.
Physical examination of the SGA infant must include a detailed search for associated abnormalities.
|Intrauterine fetal demise||Hypoxia, acidosis, infection and lethal anomaly|
|Perinatal asphyxia||Decreased uteroplacental perfusion in labour
chronic fetal hypoxia-acidosis
|Hypoglycemia||Decreased tissue glycogen stores, decreased gluconeogenesis and high glucose requirements|
|Polycythemia -hyperviscosity||fetal hypoxia with increased erythropoietin production|
|Hypothermia||Large surface area, poor subcutaneous fat stores|
|Respiratory distress||intrauterine pneumonia, meconium aspiration syndrome, PPHN|
Investigations are required to
At Delivery: Place promptly under a radiant warmer and dry. Infants with severe SGA, particularly in association with fetal distress, are at risk of aspiration of meconium , hypoxaemia, hypotension, mixed metabolic and respiratory acidosis and persistent pulmonary hypertension.
Hypothermia: Nurse in a thermoneutral environment
Hypoglycemia: Monitor blood glucose and commence early enteral feeds or intravenous glucose infusion.
Necrotisingenterocolitis: Infants, particularly preterm SGA, found to have placental insufficiency and abnormal umbilical artery Doppler studies may be at particular risk of developing NEC or gastrointestinal perforation. Enteral feeding should be increased gradually.
Principally determined by the cause.
Postnatal physical growth:
Symmetric SGA - smaller and relatively under weight throughout life.
Asymmetric SGA - accelerated velocity of growth ("catch up growth") in first 6 months and normal development.
Term SGA - no increase risk of severe neurologic morbidity compared to term AGA infants. However increased hyperactivity, short attention span and learning problems
Preterm SGA - Minor neurologic abnormalities more common than in preterm AGA infants.
Avery GB, Fletcher MA, MacDonald MG, eds. Neonatology. 5th ed. Philadelphia, Pa: Lippincott Williams & Wilkins, 1999:411-444.
Rennie JM, Roberton NRC (Eds). Textbook of Neonatology, 3rd edition. Churchill Livingstone , Edinburgh, 1999.
Patti J Thureen, Marianne S Anderson and William W. Hay, Jr. Small for gestational age, NeoReviews; 2001; E139-e149.