Percentile / SDS. z = ((X/M)L − 1) / (L·S) from embedded LMS tables.
Projected adult height. The height at 20 years on the child's current z-score — i.e. assuming they keep tracking the same centile.
MPH. (father + mother + 13)/2 for boys, (father + mother − 13)/2 for girls. The target range is MPH ± 8.5 cm (Tanner), roughly the 3rd–97th centile of expected adult heights.
Reference. WHO Child Growth Standards 2006 (0–5 y) and CDC 2000 stature-for-age (2–20 y), blended 24–30 months. Singapore's HPB recommends WHO for 0–5 y; Singapore height-for-age LMS parameters are not openly published, so CDC is used above 2 y.
Head circumference — Weaver curve. Implements Weaver & Christian, J Pediatr 1980;96:990–4. SS = (OFC − mean)/SD from the Nellhaus table reproduced as their Table I (birth–18 y); parents standardised on the 18-y row (male 55.95 ± 1.34, female 54.94 ± 1.40 cm). Child SS is read against midparental SS on their Fig. 2 regression (slope h² = 0.45, Table II), residual SD √(1 − 0.45²/2) = 0.948, normal limits ±1.90 SS. Validated against the paper's worked example: child 49.5 cm at 9 mo → SS +2.93, parents +2.65 / +2.90, midparental +2.78, limit +3.14 → normal, as the paper concludes.
Population centile. WHO 2006 HC-for-age (0–5 y) or China 2013 urban (Li et al., PLOS ONE 2013;8:e59569, 0–6 y). Chinese LMS taken from Table 4 and validated by recomputing every printed −2/−1/median/+1/+2 SD value; all 220 agreed within 0.10 cm.
Ethnicity caveat. HC varies by population far more than height. At 1 month the share below −2 SD on WHO was 6–14% in Japan/China vs 1–3% in Europe (expected 2.3%) — WHO over-flags microcephaly in East Asian neonates; after age 1 the Chinese reference sits above WHO at −2 SD, so WHO may under-flag. Nellhaus (1968) is largely Caucasian — the parental comparison is the robust part, not the absolute SS.
Screening tool only. Not a diagnostic device. Interpretation — pubertal stage, bone age, growth velocity, secular trend — requires a clinician.