We investigated the factors associated with weight gain in infancy by using a large representative sample from the UK population: the results suggest that the feeding characteristics of the infant are the dominant factors, rather than the socioeconomic status or the educational attainment of the mother. The strengths of the study are the use of a large well‐characterised representative sample and prospectively collected feeding data, avoiding many of the methodological weaknesses of hospital and clinic‐based samples and of retrospective data collection. The study is limited by the feeding data being derived from maternal report at the time of an ALSPAC questionnaire (4 weeks, 6 months and 15 months), whereas the weight data were collected at routine health service contacts (birth, 8 weeks and 9 months).
In the first 8 weeks, maternal age and height had an influence on early growth, but infant feeding difficulties were important, particularly weak sucking. There may be two underlying explanations for this association: oral–motor dysfunction11,12,13
or differences in the infant's appetite.14,15
After age 8 weeks, weight gain was also related to maternal height, and the over‐representation of Asian infants in the slowest growing 5% is also probably a consequence of shorter mothers (but could be a reflection of different infant feeding practices). The most important postnatal influences on growth were the efficiency in feeding, ability to successfully take solids and duration of breast feeding. Although these symptoms were reported by parents, who also influenced the timing of weaning, our results are consistent with behavioural studies15
reporting that children with FTT are fed as much and as frequently as controls but tend to refuse or reject offered food more often. An alternative explanation is that mothers may sense that the infant is not ready to wean (eg, not demanding solids, or showing immature oral–motor skills when offered tastes of solid food), and they continue to breast feed.
Observational studies have generally shown an association between prolonged breast feeding and slower weight gain.16
Evidence from the only relevant randomised controlled trial on breast feeding17
suggests that infants with lower appetites grow more slowly and hence are satisfied with breast milk for longer. However, it is debatable if such slow‐growing breast‐fed infants are at an overall disadvantage over the life course,18
as slow growth during infancy may actually have a long‐term beneficial effect on reducing the risk of obesity and cardiovascular disease in adulthood.19
These results have several implications for clinical practice: firstly, a reminder that the early onset and persistence of slow or difficult feeding may be a warning of inadequate nutritional intake and possible growth faltering; and secondly, the importance of supporting parents in weaning their infants at an appropriate time developmentally. The World Health Organisation (http://www.who.int/child‐adolescent‐health
) now recommends that mothers should be encouraged to exclusively breast feed and postpone the introduction of solids until age 6 months. However, the developmental “window” to wean on to solids is short: previous work from ALSPAC20,21
has shown that infants unable to take lumpy solids at 9 months were more likely to have continuing feeding difficulties and poor weight gain in the second year of life. Infants who are still predominately breast feeding at age 9 months are likely to have smaller appetites and may have difficulties taking solids; these infants require careful assessment and their mothers need sensitive support to persist in offering weaning foods of appropriate consistency and variety.
Further research using this longitudinal study will clarify whether early feeding problems leading to growth faltering is a marker for persisting neurological abnormalities and whether it is associated with developmental difficulties later in childhood.
What is already known on this topic
- Failure to thrive is a term widely used to describe infants whose growth is relatively poor.
- Most research on the topic has been based on samples derived from hospital clinics using data collected retrospectively.
What this study adds
- Factors associated with failure to thrive included sucking problems in the first few weeks, difficulties in weaning on to solids at age 6 months and reliance on breast feeding to 9 months. No associations were found with markers of social class and parental education.
- This study challenges the perception that failure to thrive is usually a reflection of social deprivation or neglect, and implies that early feeding difficulties, as a marker of subtle neurological impairment or poor appetite, are the precursors of subsequent poor weight gain.