Growth Charts & Anthropometry

Growth is the single most sensitive index of child health — a faltering line on a chart often precedes any clinical sign of disease. This topic is high-yield for NEET PG because it tests exact norms, z-score cut-offs, SAM/MAM criteria, and the practical interpretation of WHO and IAP charts used daily in Indian paediatrics.

Why anthropometry matters

Anthropometry is the measurement of body dimensions to assess nutritional status and growth. The four core parameters are weight, length/height, head circumference, and mid-upper arm circumference (MUAC). Serial measurements plotted on a growth chart are vastly more informative than a single reading, because growth velocity (the trend) reveals chronic or acute insults before absolute values cross a threshold.

High-yield: Weight is the most sensitive indicator of acute malnutrition; height (length) reflects chronic malnutrition; head circumference reflects brain growth. A flat or falling weight curve ("growth faltering") is an early red flag even when the child is still within normal percentiles.

Normal growth norms by age

Memorising the reference milestones is the most repeatedly tested chunk of this topic.

Weight

Age	Weight rule	Approx value
Birth	Reference	3 kg (term)
3–4 months	Doubles birth weight	6 kg
1 year	Triples birth weight	9 kg
2 years	Quadruples birth weight	12 kg
3 years	—	~14 kg
5 years	Doubles 1-year weight	~18 kg
7 years	—	~22–23 kg
10 years	—	~30 kg

Weight gain pattern: physiological weight loss of up to 10% in the first week (regained by 10–14 days) → then 25–30 g/day in the first 3 months → 20 g/day in months 3–6 → progressively slower.

Weale's / Indian formula for weight (1–6 yr): Weight (kg) = (Age in years × 2) + 8.

High-yield: Birth weight doubles by 5 months, triples by 1 year, quadruples by 2 years. This is among the most frequently asked single facts in paediatric nutrition.

Length / height

Age	Length/Height
Birth	50 cm
1 year	75 cm (50% increase over birth)
2 years	87–88 cm
3 years	95 cm
4 years	100 cm (≈ doubles birth length)

After 2 years, height gain is ~6–7 cm/year until puberty. Up to 2 years length is measured supine (infantometer); from 2 years upright stadiometer is used — supine length reads ~0.7 cm more than standing height.

Mid-parental height (target height):

• Boys = [(Father's height + Mother's height) + 13 cm] ÷ 2
• Girls = [(Father's height + Mother's height) − 13 cm] ÷ 2
• Target range = mid-parental height ± 8.5 cm.

Head circumference (occipitofrontal circumference, OFC)

Age	Head circumference
Birth	35 cm
3 months	40 cm
6 months	43 cm
1 year	47 cm
2 years	49 cm
12 years	~52 cm (near adult)

Growth pattern: 2 cm/month for first 3 months → 1 cm/month for next 3 → 0.5 cm/month for next 6. Net gain in year 1 ≈ 12 cm.

High-yield: At birth, head circumference (35) > chest circumference (33). They become equal at about 6–12 months, after which chest exceeds head. A persistently larger head beyond infancy suggests malnutrition (poor chest/muscle growth) or hydrocephalus.

Mnemonic for OFC ("3-9-12-2-6-7"): 35 cm at birth, then add to reach 47 at 1 yr; or remember "43 at 6 months, 47 at 1 year, 49 at 2 years."

Z-scores, percentiles & SD

WHO charts use z-scores (standard deviation scores); IAP/clinical charts often use percentiles. A z-score expresses how many SDs a measurement lies from the median of the reference population.

Z-score	Approx percentile
0 (median)	50th
−1 SD	~15th
−2 SD	~3rd
−3 SD	<1st (~0.1)
+2 SD	~97th

The three classical indices (Waterlow/WHO):

1. Weight-for-age (WFA) → composite "underweight"; cannot distinguish acute vs chronic.
2. Height-for-age (HFA) → stunting = chronic/past malnutrition.
3. Weight-for-height (WFH) → wasting = acute/current malnutrition.

Stepwise interpretation flow: Plot weight, height, WFH/BMI → check z-score → < −2 SD = moderate, < −3 SD = severe → then classify: low HFA → stunting; low WFH → wasting; low WFA → underweight.

High-yield: Wasting = acute (weight-for-height ↓), Stunting = chronic (height-for-age ↓). A child can be stunted but not wasted (chronic adaptation) — this is a classic exam discriminator.

SAM and MAM — the WHO criteria

Severe Acute Malnutrition (SAM) and Moderate Acute Malnutrition (MAM) definitions are extremely high-yield and frequently misremembered.

Parameter	MAM	SAM
Weight-for-height z-score	−3 to <−2 SD	< −3 SD
MUAC (6–59 months)	11.5 to <12.5 cm	< 11.5 cm
Bilateral pitting oedema	Absent	Present (any grade) = SAM by definition
Appetite	Usually preserved	May fail appetite test

High-yield: MUAC < 11.5 cm or WFH < −3 SD or bilateral pedal oedema = SAM, regardless of other parameters. The presence of nutritional (bilateral, pitting) oedema alone classifies a child as SAM (oedematous SAM / kwashiorkor).

MUAC thresholds (6–59 months) mnemonic — traffic lights:

• Red: < 11.5 cm → SAM
• Yellow: 11.5–12.5 cm → MAM (at risk)
• Green: ≥ 12.5 cm → normal

MUAC is age-independent between 1–5 years (changes little), making it an excellent rapid field/community screening tool (Shakir's tape, Bangle test).

Complicated vs uncomplicated SAM (determines facility vs community management):

• Complicated SAM → poor appetite, medical complication (severe oedema +++, hypoglycaemia, hypothermia, dehydration, severe anaemia, sepsis, lethargy) → inpatient (NRC/hospital).
• Uncomplicated SAM → good appetite, alert, no complication → community-based management (CMAM) with RUTF.

Pathophysiology of malnutrition (kwashiorkor vs marasmus)

Feature	Marasmus	Kwashiorkor
Primary deficit	Energy (calorie)	Protein (relative)
Oedema	Absent	Present (pitting)
Weight	Severely ↓ (<60%)	Often masked by oedema
Subcutaneous fat	Markedly lost ("old man face")	Partly preserved
Skin/hair	Normal-ish	Flaky-paint dermatosis, flag sign, hypopigmented sparse hair
Liver	Normal	Enlarged, fatty (↓ apoprotein synthesis)
Appetite	Preserved (hungry)	Poor
Albumin	Near normal	Low

High-yield: Flaky-paint dermatosis, pedal oedema, hepatomegaly, and irritable apathy → kwashiorkor. Wizened "old-man" facies with no oedema, ravenous appetite → marasmus. Marasmic-kwashiorkor = oedema + severe wasting (<60% with oedema).

WHO vs IAP growth charts (Indian context)

This comparison is frequently examined because India uses both.

Aspect	WHO 2006 charts	IAP charts
Type	Growth standard (prescriptive — how children should grow)	Growth reference (descriptive of Indian children)
Population	Multi-ethnic (incl. India), exclusively breast-fed, optimal conditions	Indian affluent/urban children
Recommended age	0–5 years	5–18 years
Unit	Z-scores	Percentiles (3rd, 50th, 97th)
BMI cut-offs (adolescents)	—	23 & 27 adult-equivalent lines for overweight/obesity

High-yield: Government of India / IAP recommends WHO 2006 standards for 0–5 years and IAP 2015 charts for 5–18 years. WHO is a standard (single best benchmark); IAP is a reference for older children where WHO data are limited.

For overweight/obesity in Indian children (IAP 2015), the adult-equivalent BMI cut-offs of 23 (overweight) and 27 (obesity) are extrapolated downward as percentile-based adult equivalent lines — a deliberately Indian adaptation given higher metabolic risk at lower BMI.

Catch-up & catch-down growth

Catch-up growth = growth velocity above the normal range for age after a transient growth-limiting insult (illness, malnutrition) is removed, allowing the child to return to its original (genetic) channel.

• Seen after correction of malnutrition, treatment of coeliac/hypothyroidism, post-illness recovery.
• During nutritional rehabilitation of SAM, expected weight gain is >10 g/kg/day = good, 5–10 = moderate, <5 g/kg/day = poor (needs reassessment).
• Catch-down growth = downward percentile crossing in the first 2 years as a large-for-gestation or genetically smaller infant settles into its true channel — normal if the trajectory then stabilises.

High-yield: A child crossing percentile lines upward after illness/nutrition correction = catch-up growth (physiological, reassuring). Crossing lines downward after age 2 = pathological growth faltering until proven otherwise.

Clinical assessment & investigation of choice

Investigation/assessment of choice is the serial growth chart itself — anthropometry plotted over time. Key practical points:

• Weighing: infants on a beam/pan scale (accuracy 10 g), older children standing scale (100 g).
• Length: infantometer (<2 yr, supine); height: stadiometer (≥2 yr, standing).
• OFC: non-stretchable tape over the maximal occipitofrontal diameter.
• MUAC: left arm, midpoint between acromion and olecranon, arm relaxed.
• BMI for ≥2 years and adolescents (weight kg ÷ height m²) plotted on age-/sex-specific charts.

Bone age (left wrist/hand X-ray, Greulich-Pyle or Tanner-Whitehouse) helps differentiate constitutional delay (delayed bone age) from familial short stature (normal bone age) and assess remaining growth potential.

Gomez classification (weight-for-age, % of expected): ≥90% normal; 75–90% Grade I; 60–74% Grade II; <60% Grade III. IAP classification uses ≥80% normal; 70–80% Grade I; 60–70% Grade II; 50–60% Grade III; <50% Grade IV. Waterlow combines stunting (HFA) and wasting (WFH).

Management / nutritional rehabilitation of SAM

WHO 10-step management of complicated SAM (inpatient), in two phases — stabilisation then rehabilitation:

Stabilisation: 1) Treat/prevent hypoglycaemia, 2) hypothermia, 3) dehydration (use ReSoMal, not standard ORS — lower sodium, higher potassium), 4) correct electrolytes, 5) treat infection (broad-spectrum antibiotics empirically), 6) correct micronutrients (withhold iron initially), 7) cautious feeding (F-75, low protein/low energy).

Rehabilitation: 8) catch-up growth (F-100 or RUTF), 9) sensory stimulation, 10) prepare for follow-up.

High-yield: In SAM management, iron is withheld in the stabilisation phase (started only in rehabilitation) — free iron worsens infection and oxidative stress. Use ReSoMal for rehydration. F-75 to stabilise, F-100 to grow. Beware refeeding syndrome (hypophosphataemia, hypokalaemia, hypomagnesaemia) on aggressive refeeding.

Complications

• SAM: hypoglycaemia, hypothermia, dehydration/shock, electrolyte disturbance, refeeding syndrome, sepsis, vitamin A deficiency (xerophthalmia/keratomalacia → blindness), anaemia, developmental delay, high mortality.
• Chronic stunting: irreversible loss of linear growth, impaired cognition and school performance, lower adult productivity, intergenerational cycle (low-birth-weight offspring).
• Microcephaly (OFC < −3 SD or <3rd percentile): TORCH infections, Zika, genetic syndromes, perinatal insult.
• Macrocephaly (OFC > +2 SD / >97th): hydrocephalus, subdural collection, benign familial macrocephaly, storage disorders.

Key differentials

• Short stature: familial short stature (normal bone age, normal velocity) vs constitutional growth delay (delayed bone age, delayed puberty, eventually normal height) vs pathological (hypothyroidism, GH deficiency, Turner, coeliac disease, chronic disease).
• Failure to thrive (FTT): organic (malabsorption, cardiac, renal, chronic infection, TB) vs non-organic (psychosocial deprivation, feeding error) — assess weight crossing ≥2 major percentile lines downward.
• Oedema in a child: kwashiorkor vs nephrotic syndrome vs cardiac/hepatic — kwashiorkor oedema is bilateral, pitting, dependent, with dermatosis/hair changes.

Recently asked / exam angle

• Direct factual recall: "Birth weight doubles by ___?" (5 months), "triples by ___?" (1 year). "Head circumference at 1 year?" (47 cm).
• MUAC cut-off for SAM (< 11.5 cm) — repeatedly asked; do not confuse with 12.5 (MAM threshold).
• WFH z-score for SAM (< −3 SD) and the fact that bilateral oedema = SAM regardless of weight.
• WHO vs IAP chart age ranges (WHO 0–5 yr standard; IAP 5–18 yr reference) and "standard vs reference" terminology.
• Image-based MCQs: identifying kwashiorkor (flaky-paint, oedema, flag sign) vs marasmus (old-man facies).
• F-75 vs F-100 roles, ReSoMal, and "which is withheld initially in SAM" (iron).
• Wasting vs stunting (acute vs chronic) — classic single-best-answer discriminator.
• Head vs chest circumference crossover age (6–12 months).

Rapid revision

1. Birth weight: doubles 5 mo, triples 1 yr, quadruples 2 yr; loss up to 10% in week 1, regained by day 14.
2. Length: 50 cm birth → 75 cm at 1 yr → 100 cm at 4 yr; after 2 yr ~6–7 cm/yr.
3. OFC: 35 cm birth → 47 cm at 1 yr → 49 cm at 2 yr; head>chest at birth, equal by 6–12 mo.
4. SAM = WFH < −3 SD OR MUAC < 11.5 cm OR bilateral pitting oedema.
5. MAM = WFH −3 to −2 SD OR MUAC 11.5–12.5 cm.
6. MUAC traffic light: <11.5 red (SAM), 11.5–12.5 yellow (MAM), ≥12.5 green; age-independent 1–5 yr.
7. Wasting = acute (WFH↓); Stunting = chronic (HFA↓); Underweight = WFA↓.
8. WHO 0–5 yr (standard, z-scores); IAP 5–18 yr (reference, percentiles).
9. Kwashiorkor = oedema + flaky-paint + fatty liver + poor appetite; Marasmus = severe wasting, no oedema, hungry.
10. SAM treatment: F-75 stabilise → F-100 grow, ReSoMal for rehydration, iron withheld initially, watch refeeding syndrome.
11. Good catch-up weight gain in SAM = >10 g/kg/day.
12. Mid-parental height: boys (M+F+13)/2; girls (M+F−13)/2; target ± 8.5 cm.