• About us
• Guideline index
• Feedback

Print version

 

Small for Gestational Age Infants

• Definition
• Types
• Aetiology
• Physical Examination
• Problems in SGA
• Investigations
• Management
• Outcome
• References

Definition

Small for gestational age infants are defined as having a birth weight more than 2SD below the mean or less than the 10^th percentile of a population specific weight versus gestational age plot.

Types

Symmetric: Weight, head circumference and length all below the 10^th percentile. Brain growth may be limited.

Causes

intrinsic fetal causes intrauterine infection severe placental insufficiency constitutionally small infant

Asymmetric: Weight below the 10^th percentile but head circumference and length relatively preserved. Brain growth relatively spared.

Causes

interference with placental function or maternal health in 3rd trimester.

Infants whose weight is greater than the 10^th 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.

Aetiology

Fetal	chromosome disorders (eg Trisomy 21, Trisomy 18) chronic fetal infection (eg CMV, Rubella, Syphilis, Toxoplasmosis) congenital malformations: including congenital heart disease, diaphragmatic hernia, tracheo-oesophageal fistula syndrome complex radiation multiple gestation relates more to placental limitation rather than intrinsic baby problem
Mother	pregnancy induced hypertension hypertension or renal disease or both hypoxaemia (high altitude, cyanotic cardiac or pulmonary disease) malnutrition or chronic illness drugs (narcotics, alcohol, cigarettes, cocaine, antimetabolites)
Placental	decreased placental weight or cellularity or both decrease in surface area, infarction villous placentitis (bacterial, viral, parasitic) tumour (chorioangioma, hydatiform mole) placental separation twin to twin transfusion syndrome
Constitutional	familial and racial background

Physical Examination

Physical examination of the SGA infant must include a detailed search for associated abnormalities.

• dysmorphic features "unusual" facies
  • abnormal hands and feet
  • abnormal palmar creases
  • in addition to gross anomalies
    
    
• ocular disorders, such as
  • cataracts
  • cloudy cornea
  • chorioretinitis
    
    
• features of intrauterine infection
  • hepatosplenomegaly 
  • jaundice
  • blueberry-muffin rash

Problems in SGA

Problem	Pathogenesis
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

Investigations are required to

• screen for hypoglycemia
  
  
• assess the infant according to clinical signs
  • polycythemia  and hypocalcaemia are more common.
  • if respiratory distress present, ABG and Chest X-ray.
    
    
• establish the cause of growth restriction
  • intrauterine infection suspected; check maternal TORCH serology and screen infant urine and saliva for CMV (further investigation will be required if suspicion confirmed).
  • if dysmorphic; genetic consultation and chromosome studies 
  • if showing signs of withdrawal urine for drug screen.
  • ultrasonography and echocardiography, if clinically indicated

Management

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.

Polycythemia:  Partial volume exchange may be required for symptomatic infants.

Outcome

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.

Neurodevelopmental outcome:

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.

References

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.

Please remember to read the disclaimer.
We welcome your Feedback.