Normal growth from fetal life through adolescence — formative SAQs

SAQ 1 (10)

A 7-year-old boy is referred because he is “the smallest in his class.” Height is on the 3rd centile. Weight is on the 10th. He tracks parallel to the 3rd height centile over 18 months. Both parents are short. Examination is normal. Puberty has not begun. [6]

1. Outline the infancy–childhood–puberty model of linear growth and state which phase dominates at age 7. (3) [3]
2. List four features that support familial short stature rather than pathological short stature. (4) [6]
3. State when idiopathic short stature is an appropriate residual label. (3) [5]

Model answer

ICP at age 7. Infancy growth is largely nutrition-driven; childhood growth depends on the GH–IGF-1 axis; puberty adds sex-steroid drive and a spurt. At age 7, childhood-phase GH–IGF-1 biology dominates. [3]

Familial short stature features. Short parents / mid-parental height consistent with current channel; normal growth velocity (parallel tracking); normal examination without disproportion or dysmorphism; delayed evaluation not forced by red flags (systemic symptoms, falling height velocity). Bone age often near chronological age in classic familial short stature teaching, in contrast to constitutional delay. [6]

ISS. Idiopathic short stature is residual after complete evaluation for short stature, including exclusion of alternative causes and stimulated GH testing in consensus frameworks — not a first-glance clinic label for every child near the 3rd centile. [5]

SAQ 2 (10)

You review serial growth in clinic. [1]

1. Distinguish a growth standard from a growth reference, naming one example of each. (3) [1] [2]
2. In the US recommendation set, which charts are preferred under 24 months and from 2 years? What WHO screening extremes are recommended (±SD)? (3) [2]
3. Define SGA versus fetal growth restriction and state why catch-up surveillance matters. (4) [4]

Model answer

Standard vs reference. A standard describes how children should grow under favourable conditions (WHO Child Growth Standards 0–5 years). A reference describes how a population did grow (CDC 2000 charts; also WHO 5–19 as a reference for older children). [1] [2]

US chart allocation. WHO charts for ages under 24 months; CDC charts from 2 years. When screening on WHO charts, use about ±2 SD (near 2.3rd and 97.7th percentiles). [2]

SGA vs FGR. SGA is a birth-size label (commonly weight below a gestation- and sex-specific threshold such as the 10th centile). FGR describes restricted fetal growth as a process. Many SGA infants catch up; those who do not need structured etiology review and long-term follow-up per international SGA consensus principles. [4]