Failure to thrive and faltering growth: diagnostic approach

You will hear two labels. Failure to thrive (FTT) is still common in US and older exam stems. Faltering growth is the preferred UK NICE language. They describe the same clinical problem: a child whose weight gain, and sometimes length or overall growth, is not following an expected trajectory. Neither label is a final diagnosis. Both are a prompt to find mechanism and threat. ^{[1] [3] [5]}

Measurement technique, chart choice and z-score maths live on the sister page Growth measurement, charting and interpretation. This page assumes you can re-measure and re-plot. It focuses on what the plot means and what you do next. ^{[10] [11]}

Overview & Definition

A caregiver brings a nine-month-old because “clothes are still huge” and the health visitor is worried. The weight sits on the 2nd centile. That single point is not yet a diagnosis. You need prior points, correct age on the chart, and a sense of velocity. A child who has always tracked the 2nd centile with a healthy feed and exam is different from a child who fell from the 50th to the 2nd over three months. ^{[1] [4] [5]}

Olsen’s review makes the uncomfortable point clearly: FTT has never had one universal definition. Clinics use weight-for-age cut-offs, weight-for-length or BMI thresholds, and downward centile crossing. Different rules catch different children. In practice, fellowship answers should name the pattern you see, not hide behind a single magic percentile. ^[5]

NICE-aligned teaching uses faltering growth for children whose weight gain is slower than expected. Practical primary-care guides still use FTT for the same clinical task: recognise inadequate growth, find cause, support nutrition, and protect the child. ^{[1] [2] [3]}

References20ShowHide

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15. [15]Mills E Association between caregiver concern for clinical deterioration and critical illness in children presenting to hospital: a prospective cohort study Lancet Child Adolesc Health, 2025.PMID 40451224
16. [16]Lipkin PH Promoting Optimal Development: Identifying Infants and Young Children With Developmental Disorders Through Developmental Surveillance and Screening Pediatrics, 2020.PMID 31843861
17. [17]Kuo DZ Recognition and Management of Medical Complexity Pediatrics, 2016.PMID 27940731
18. [18]Katz AL Informed Consent in Decision-Making in Pediatric Practice Pediatrics, 2016.PMID 27456510
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