New insights into the postnatal growth of infants born 'idiopathic' small for gestational age

Infants born small for gestational age (SGA) are defined as those with a birth weight and/or birth length below two standard deviations for gestational age. Postnatal catch-up growth is absent in 8-12% of children born SGA and these children achieve adult heights far below their target height. The objectives of our retrospective study were to confirm the prevalence of catch-up growth and to refine the kinetics of the catch-up process. The 'Lyon series' of patients consisted of 179 children with 'idiopathic' SGA, of whom 8% did not achieve catch-up growth (i.e. their height remained below -2 SD throughout the study). The number of days that the mother was hospitalized before delivery was found to be significantly correlated with lack of catch-up growth. Maternal hypertension, term delivery and postnatal parenteral nutrition were also associated with lack of catch-up growth, but the relationship was not significant. In addition, an oscillatory growth velocity pattern was observed in boys and girls born SGA, with alternating periods of growth acceleration and deceleration. This suggests that catch-up growth is regulated in a sophisticated way by the hypothetical 'Somatostat', although further confirmation of this process is needed.