Children born small for gestational age (SGA) : growth and clinical assessment at age 4 to 6 years and treatment with recombinant growth hormone in children born SGA without catch up growth

Abstract

Small for gestational age (SGA) is a descriptive term used to describe a baby who is bom smaller than expected for its gender and gestation. By international consensus the current definition is a birth weight ≥2 standard deviation scores (SDS) below the mean for that gender and gestation using appropriate population reference standards. As this approximates to the 2nd centile we would expect the incidence of SGA to be roughly 2% of all births. Although the definition has many limitations, given that fetal growth is a spectrum, it appears to be the most appropriate to detect those infants born pathologically rather than constitutionally small. As being born SGA is associated with adverse perinatal outcomes, postnatal growth failure, short stature and future adult health problems, this is an area which has attracted widespread interest and research across a variety of disciplines ranging from obstetrics, neonatology and paediatrics to epidemiology and public health. Various socioeconomic and lifestyle factors such as smoking and ethnicity have been identified as risks for SGA; however, there are also a variety of medical/obstetric characteristics which contribute to poor fetal growth. The medical management of children born SGA has been a subject of intense debate, controversy, and clinical challenge. This is due in part to inconsistent diagnostic and treatment criteria and poor understanding of the mechanisms that lead to inappropriate postnatal weight gain and insulin resistance in some, and persistent short stature in others. Possible genetic factors such as growth hormone receptor genotype, mutations in genes involved in the insulin-like growth factor (IGF) pathways, insulin receptors or as-yet-unidentified isolated gene defects are proposed to play a role. Human epidemiological data have demonstrated that adaptive responses made by the fetus in response to a poor nutritional environment may be deleterious to adult health if the postnatal nutritional environment is one of nutritional excess. In the light of current growing prevalence of childhood obesity there is evidence to suggest that some of the metabolic consequences of intrauterine growth retardation in children born SGA can be mitigated by ensuring early appropriate catch-up growth, while avoiding excessive weight gain. Current infant nutritional practices are now the subject of increasing interest especially in preterm infants although little is known on what is optimal growth velocity in the context of antenatal growth restriction.