Integrating Fetal and Infant Growth

AIM: The Infancy-Childhood-Puberty growth model translates the human linear growth curve into simple mathematical expressions. We will use this model to explore the integration of fetal and infant growth. METHODS: The infancy component was extrapolated to fetal life, and the introduction of the childhood component by the end of the first year of life was investigated. RESULTS: The infancy component of the growth model portrays the uninterrupted continuation of fetal growth up to the first six months of life. The childhood component starts between six and 12 months of age. The onset of the childhood component is characterized by an abrupt increase in the growth rate, along with a significant increase in serum insulin-like growth factor I and insulin-like growth factor binding protein 3 levels. CONCLUSION: The infancy component of the growth model represents the action of nutrition and insulin-like growth factor I and progresses independently of growth hormone. The onset of the childhood component represents the unknown age at which growth becomes dependent on growth hormone.