Risk factors for intra-uterine growth restriction (IUGR) include pre-natal factors (maternal stature and nutritional status), events during pregnancy (e.g. multiple births, infections) as well as behavioural factors (e.g. illicit drug use, short intra-pregnancy interval). IUGR in early gestation tends to result in a symmetrical growth restriction, such that length, weight and head circumference are equally impacted. Late-stage IUGR produces more asymmetrical effects: different organs are affected at different times.
IUGR can lead to circulatory and metabolic changes including increases in hypoxia and lactic acidemia, which can reduce umbilical flow. These conditions can in turn lead to hyperglycemia, improper cardiopulmonary development, infarctions and cerebral hypoxia. Asphyxia owing to IUGR accounts for a large proportion of stillborn babies.
SGA babies have altered metabolisms and often have fasting hypoglycemia. They have little hepatic glycogen and few fatty acids in circulation with reduced ketone formation, which suggests that fatty acid oxidation is impaired. An important consideration for SGA babies is therefore temperature regulation as they have small adipose reserves and comparatively large surface areas.
Infants who are well fed show increased oxygen consumption and can catch up on growth. However, Professor Bhatia stresses the important message that over-nutrition of SGA babies must also be avoided and that the body image of a healthy baby may need to be reconsidered.