Growth, Development and Behavioral Pediatrics
This domain tests whether you can plot and interpret growth, recognise deviations in developmental trajectory, and screen for behavioral disorders. The exam expects numbers - milestone ages, percentile cutoffs, growth velocities.
Growth
- Use WHO charts from birth to 2 years and CDC charts from 2 to 20 years. Birth weight doubles by 4-5 months, triples by 12 months and quadruples by 24 months.
- Head circumference is about 35 cm at birth and 47 cm at 1 year; measure occipitofrontal circumference at every visit under age 3.
- Short stature means height below the 3rd percentile or below -2 SD. Calculate mid-parental height (boys: [father + mother + 13]/2; girls: [father + mother - 13]/2; target range ±8.5 cm) and document growth velocity. Velocity under 5 cm/year after age 4 requires investigation.
- Crossing two major centile lines downward suggests growth faltering.
Development
- Social smile at 6 weeks, head control at 3 months, sitting at 6-8 months, walking at 12-15 months, 50 words and two-word phrases by 18-24 months, three-word sentences by 3 years.
- Loss of previously acquired skills is regression, not delay, and demands urgent evaluation.
Behavior
- ADHD requires at least six inattentive or hyperactive-impulsive symptoms for at least six months, present before age 12, in two or more settings, with clear impairment.
- Screen for autism with M-CHAT at 18 and 24 months. Absent pointing, no response to name and no pretend play by 18 months are red flags.
Worked example
An 18-month-old says five words, does not point, and does not turn to his name. Reasoning: this is language delay plus impaired joint attention, not isolated speech delay. Order audiology, M-CHAT and a developmental assessment concurrently instead of adopting a wait-and-see approach.
Traps
Measuring length lying down after age 2; omitting head circumference; and calling short stature familial without a growth velocity calculation.