- Intrauterine growth retardation (IUGR), defined as birth weight less than 2 standard deviations below the mean by Usher and McLean Deficient "catch-up" growth (stature less than 5th percentile on growth chart after age 18 months) Normal or elevated circulating concentrations of insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3) IGF-I or IGFBP-3 within or above the 95th percentile confidence interval for age No other clinical explanation for poor prenatal and postnatal growth No IUGR due to maternal toxemia, endocrine disease, gastrointestinal disease, significant heart disease, or chromosomal abnormalities No other condition known to retard growth