A Trial to Evaluate the Correlation Between Spontaneous Catch-up Growth, Clinical Response to Saizen (Recombinant Human Growth Hormone, r-hGH) and Gene Expression Profiling in Children Small for Gestational Age (SGA)

Inclusion Criteria: * SGA at birth (defined as a length at birth equal or below the tenth percentile according to the Italian reference table of Bertini and Fabris) * Age of 24 Months * Caucasic * Born at term (i.e. after the 37th completed week of gestation) * Height equal or below (Group A) or up (Group B) the third percentile at the age of 24 months according to the Tanner reference table * Sufficient GH secretion (more than 10 nanogram (ng)/milliliter (ml)) at least to one of the tests commonly used at that age (glucagon, Levo-dopa, arginine, clonidine, Growth Hormone Releasing Hormone (GHRH), GH integrated secretion) * Normal level of Thyroid-stimulating hormone (THS), Free Triiodothyronine (FT3), Free Thyroxine (FT4), Insulin-like growth factor 1(IGF-1), insulin and haemoglobin A1c (HbA1c) * Normal level of Immunoglobulin A (IgA) * Children parents willing to comply with the protocol for the whole duration of the study * A written Informed Consent before the baseline visit must be obtained from the parent(s) / legal guardian(s) Exclusion Criteria: * Congenital malformations (including Silver-Russel syndrome) * Known abnormal karyotype, especially in girls * Twins * Severe psychomotor retardation * Previous or ongoing treatment with anabolic steroids or r-hGH * Treatments interfering with the immune system (including bacterial lysate) * Severe chronic illnesses * Autoimmune diseases