Paediatrics: Small for gestational age

Small for gestational age

SGA is birth weight <10th centile for gestational age. Intrauterine growth restriction (IUGR) is failure of growth in-utero that may or may not result in SGA.

• Symmetric (proportional) SGA: all growth parameters symmetrically small; suggests foetus affected from early pregnancy, e.g. chromosomal disorder or constitutional.
• Asymmetric (disproportional) SGA: weight centile < length and headcircumference. Usually because of IUGR due to insult in late pregnancy, e.g. pre-eclampsia. Asymmetric SGA infants at risk of complications.

Causes

• Constitutional, i.e. small parents (commonest).
• Restricted foetal O₂or glucose supply, e.g. placental dysfunction, maternal hypertension, multiple pregnancy, maternal illness.
• Foetal abnormality, e.g. chromosomal disorders, congenital anomalies and syndromes, congenital infection.
• Maternal substance exposure, e.g. alcohol, smoking, therapeutic or other drugs.

Complications

• Incre Risk of foetal death and asphyxia (SGA indicates foetal compromise).
• May have congenital infection, toxoplasmosis, others, rubella, cytomegalovirus, herpes virus II (TORCH) or malformation.
• Hypoglycaemia.
• Hypothermia.
• Polycythaemia.
• Necrotizing enterocolitis and/or intolerance of feeds.
• Thrombocytopenia/neutropenia/coagulopathy.
• Meconium aspiration syndrome.

Management

Ideally manage on a postnatal ward with increased ratio of midwives.

• Routine postnatal care.
• Evaluate clinically for features suggestive of underlying cause.
• Particular attention to thermal care and blood glucose monitoring.
• Observe temperature, pulse, and respiration for at least the first 48hr.
• Admit to neonatal unit if birth weight <1800g.
• Well, infants can be discharged when: they are sucking all feeds 3–4-hourly; weight gain is satisfactory (20–30g/day); body temperature is maintained at room temperature; mother is capable of caring for infant.

Prognosis

Neurodevelopmental impairments more common in SGA infants. Symmetric SGA infants often stay small. The Barker hypothesis suggests IUGR infants with a small placenta are at risk in later life of coronary disease, stroke, obesity, and hypertension.