Behaviour and weight gain in early infancy
Slow weight gain in infancy is the core sign of failure to thrive. However, it is far from clear what the cause of the slow weight gain in infancy is. Failure to thrive is mostly identified late in the first year at which time it becomes problematic to ascertain its causes retrospectively. The current study was designed to investigate weight gain and behaviour in the early weeks of infancy in a prospective study. Seventy-five eight-week old infants were recruited according to their weight gain from birth to eight weeks, and classified as having slow, average or fast weight gain. Infants and their mothers were observed during two feeds. Mother-infant interaction and sucking behaviour were assessed. In addition, mothers completed questionnaires on the infant's temperament and behaviour (such as sleeping and crying), and on their own eating behaviour and adaptation to motherhood. All infants were followed up at six months and weighed again. The follow-up weight at six months allowed the identification of infants with failure to thrive as traditionally clinically defined. Six infants were identified as failing to thrive at six months, all of which had slow weight gain from birth to eight weeks. The behaviours measured through observation and the questionnaires were investigated in relation to weight gain from birth to eight weeks and six months. No significant relationship was found between weight gain and maternal adaptation, the mother's eating behaviour or infant behaviour. One sucking behaviour parameter estimate, pause length, end, was found to be significantly related to weight gain to eight weeks. This result however, was entirely attributable to the estimates of one infant. This infant had particularly poor sucking behaviour and very slow weight gain from birth to eight weeks. Infant temperament, and in particular the infant's level of fear was related to weight gain from birth to eight weeks. Infants with higher levels of fear were more likely to have slow weight gain. The length of the feed, from which the sucking behaviour was observed, was related to weight gain, with infants with long feeds being more likely to have slow weight gain.