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Key messages

  • Outcomes for small for gestational age (SGA) infants are principally determined by cause.
  • Symmetrical SGA indicates slow development through the pregnancy and brain growth may be limited.
  • In asymetrical SGA infants head circumference and length are relatively well preserved; brain growth is relatively spared.
  • Investigations may be required to establish the cause of growth restriction.
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    In June 2023, we commenced a project to review and update the Maternity and Neonatal eHandbook guidelines, with a view to completion in 2024. Please be aware that this guideline is out of date, will not be updated and will be retired from the website at the end of 2023. In the meantime, we recommend that you refer to more contemporaneous evidence.

    Small for gestational age (SGA) infants are defined as having a birthweight more than 2SD below the mean or less than the 10th percentile for the gestational age.

    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.

    Types of SGA


    Characteristics of symmetric SGA include:

    • weight, head circumference and length all below the 10th percentile
    • slow development throughout the pregnancy
    • limited brain growth.

    Causes of symmetric SGA include:

    • chromosomal abnormalities
    • intrauterine infection
    • severe placental insufficiency
    • constitutionally small infant.


    Characteristics of asymmetric SGA include:

    • weight below the 10th percentile
    • head circumference and length relatively preserved
    • fetus has grown normally for first two trimesters
    • brain growth relatively spared.

    Causes of asymmetric SGA include:

    • interference with placental function
    • interference with maternal health in third trimester.

    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 (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.


    • Chromosome disorders: (Trisomy 21, 18, 13)
    • Chronic congenital infection: (CMVrubellasyphilistoxoplasmosis)
    • Congenital malformations: congenital heart disease, diaphragmatic hernia, tracheo-oesophageal fistula
    • Syndrome complex
    • Radiation
    • Multiple gestation relates more to placental limitation rather than intrinsic baby problem
    • Pregnancy induced hypertension
    • Hypertension, renal disease, or both
    • Hypoxaemia (high altitude, cyanotic cardiac or pulmonary disease)
    • Malnutrition or chronic illness
    • Drugs (narcotics, alcohol, cigarettes, cocaine, antimetabolites)
    • Decreased placental weight, cellularity, or both
    • Decrease in surface area, infarction
    • Villous placentitis (bacterial, viral, parasitic)
    • Tumour (chorioangioma, hydatiform mole)
    • Placental separation
    • Twin to twin transfusion syndrome
    • Familial and racial background

    Physical examination

    Physical examination should 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
      • cataracts
      • cloudy cornea
      • chorioretinitis
    • features of intrauterine infection
      • hepatosplenomegaly 
      • jaundice
      • blueberry-muffin rash.

    Problems in SGA

    Problem Pathogenesis
    Intrauterine fetal demise
    • Hypoxia
    • acidosis
    • Infection
    • Lethal anomaly
    Perinatal asphyxia Decreased uteroplacental perfusion in labour +/- chronic fetal hypoxia/acidosis
    • Decreased tissue glycogen stores
    • Decreased gluconeogenesis
    • High glucose requirements
    Polycythaemia - hyperviscosity Fetal hypoxia with increased erythropoietin production
    • Large surface area
    • Poor subcutaneous fat stores
    Respiratory distress


    Investigations for SGA include the following:

    • Placental history
    • FBE, platelet count for:
      • suspected sepsis/chronic intrauterine infection
      • unwell baby
      • plethoric baby
    • BGL screen for hypoglycaemia
    • If respiratory distress:
      • ABG
      • chest X-ray.
    • Establish the cause of growth restriction:
      • If intrauterine infection is 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.
      • Opthalmology review


    At birth


    Nurse in a thermoneutral environment.


    • Monitor blood glucose.
    • Commence early enteral feeds or intravenous glucose infusion.

    Necrotising enterocolitis (NEC)

    • 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.


    Partial volume exchange may be required for symptomatic infants. See polycythemia.


    The outcome for SGA infants is principally determined by the cause.

    Postnatal physical growth

    • Symmetric SGA are smaller and relatively underweight throughout life.
    • Asymmetric SGA accelerated velocity of growth (‘catch up growth‘) in first six months and normal development.

    Neuro-developmental outcome

    • Term SGA no increased risk of severe neurological morbidity compared with term AGA infants. However, increased hyperactivity, short attention span and learning problems may result.
    • Preterm SGA - minor neurological abnormalities are more common than in preterm AGA infants.

    More information



    • Avery GB, Fletcher MA, MacDonald MG, eds. Neonatology. 5th edn. Philadelphia, Pa: Lippincott Williams & Wilkins, 1999:411-444.
    • Rennie JM, Roberton NRC (Eds). Textbook of Neonatology, 3rd edn. Churchill Livingstone , Edinburgh, 1999.
    • Patti J Thureen, Marianne S Anderson and William W. Hay, Jr. Small for gestational age, NeoReviews; 2001; E139-e149.
    • Small for Gestational Age: Causes and Consequences
    • N Engl J Med 2009; 360:2687-2688

    Get in touch

    Clinical Guidance Team
    Safer Care Victoria

    Version history

    First published: August 2013
    Review by: August 2016

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