Biological vulnerability in infants with failure to thrive: the association with birthweight

The development of failure to thrive (FTT) is hypothesized to be caused by the interaction between biological and environmental factors. Birthweight is one biological variable thought to play a role in the infant's growth failure. In studies that enrolled infants with FTT who were full-term at birth, the reported birthweights of these infants were significantly less than healthy control infants (M = 2959 g vs. M = 3364 g), t(14) = -4.597, P < 0.000. There is growing evidence that there is a subgroup of full-term newborn infants who actually may have experienced some degree of intrauterine growth retardation but their birthweights remain above the traditional cut-off of 2500 g so that they go unrecognized. The question to consider is whether these infants are as behaviourally vulnerable as full-term infants with classic intrauterine growth retardation. It may be that this unrecognized group is at a higher risk of developing FTT. The purpose of this manuscript is to discuss birthweight as a possible precursor to the development of FTT.