Growth & Developmental Milestones

Paediatrics differs from adult medicine in having a moving normal. A heart rate of 140 is alarming in an adult and unremarkable in an infant, and the same is true of almost every parameter.

The organising tool has two halves. Growth measures the body against time; development measures function against time. And in growth failure, the order in which the measurements falter tells you the cause.

That second point is the one candidates miss. Weight, then length, then head circumference is not an arbitrary sequence. It is a hierarchy of protection, because the body sacrifices fat and muscle before it sacrifices linear growth, and it sacrifices linear growth before it sacrifices the brain.

So a child whose weight has fallen but whose height and head are normal is undernourished, and a child whose head circumference has faltered has either a very long-standing problem or a primary brain problem.

Development is assessed differently, because it is not one thing. A child can be advanced in one domain and delayed in another, which is why assessment is always across four domains rather than as a single score.

1. Reading a Growth Chart

Growth is assessed by plotting serial measurements, and the single most important principle is that a trend matters more than a point.

A child on the third centile who has always been on the third centile is probably a small normal child. A child who has fallen from the fiftieth to the third has a problem, even though the second measurement is identical.

India uses the World Health Organization growth standards from birth to five years and the Indian Academy of Pediatrics charts from five to eighteen years.

The distinction between a standard and a reference is worth understanding. The World Health Organization charts are prescriptive standards derived from healthy, breastfed children raised in optimal conditions across several countries, describing how children should grow. A reference simply describes how a given population does grow, which in a malnourished population makes stunting look normal.

Crossing centile lines downwards is faltering; crossing upwards is catch-up growth. Some centile crossing in the first two years is physiological, because birth weight reflects the intrauterine environment and the infant then finds its own genetic trajectory.

Mid-parental height estimates a child's genetic target and contextualises a low measurement, since short parents produce short children who are entirely healthy.

2. Normal Growth and Its Velocity

Certain figures are examined directly and are worth knowing precisely.

Weight loss of up to about 10 per cent in the first week is physiological, because the infant loses extracellular fluid and takes several days to establish feeding. Failure to regain birth weight by two weeks requires assessment.

Growth velocity, rather than absolute size, identifies pathology. The fastest growth occurs in infancy, slows through childhood to a steady few centimetres a year, and accelerates again at puberty.

A child growing at a normal velocity below the third centile is constitutionally small. A child growing at an abnormally slow velocity is pathologically short, even if still within the normal range, and that distinction determines whether investigation is needed.

Dentition follows a rough sequence, with the first primary teeth erupting at around six months.

3. Approaching Short Stature

Short stature is height below the third centile or more than two standard deviations below the mean, and the approach begins by dividing causes into two groups.

Proportionate short stature means the trunk and limbs are equally affected, which suggests a systemic, nutritional or endocrine cause. Disproportionate short stature suggests a skeletal dysplasia such as achondroplasia, or rickets.

Within proportionate causes, two normal variants must be separated from disease.

Familial short stature gives a child who is short, growing at a normal velocity, with a bone age matching chronological age and short parents. Constitutional delay of growth and puberty gives a child who is short with a delayed bone age, a family history of late puberty, and who will eventually reach a normal adult height.

The bone age is what separates them, and it is the single most useful investigation in short stature.

Pathological causes divide usefully by their effect on weight. Undernutrition and chronic systemic disease reduce weight before height. Endocrine causes reduce height before weight, so a short, overweight child is far more likely to have hypothyroidism or growth hormone deficiency than malnutrition.

That inversion is examined regularly and is genuinely useful clinically.

Hypothyroidism, growth hormone deficiency, Cushing syndrome and poorly controlled diabetes are the endocrine causes. Turner syndrome must be considered in any short girl, and karyotyping is indicated even without other features.

4. Faltering Growth, Head Size and Obesity

Faltering growth, the term that has replaced failure to thrive, means a sustained fall across centiles rather than a single low measurement.

The old division into organic and non-organic causes is less useful than asking a simpler question: is the child not getting enough, not absorbing enough, or not retaining enough?

Inadequate intake is much the commonest, and its causes range from poverty and feeding technique through to a cleft palate or a neurologically impaired child who cannot suck effectively. Inadequate absorption points to coeliac disease, cystic fibrosis or chronic infection. Excessive requirement or loss points to congenital heart disease, chronic renal disease or hyperthyroidism.

A careful feeding history and direct observation of a feed identify the cause far more often than investigation does, and extensive testing in a child with no other abnormality is usually unrewarding.

Head circumference is measured because it is a proxy for brain growth. Microcephaly means a head more than two standard deviations below the mean, and it may be primary, as in genetic and syndromic causes and congenital infection, or secondary to an insult such as hypoxic injury or meningitis, in which case the head was normal at birth and faltered afterwards.

Macrocephaly may be benign and familial, in which case parental head circumference is also large, or may indicate hydrocephalus, in which case the fontanelle is tense, the sutures are separated and the head is crossing centiles upwards.

Childhood obesity is now rising rapidly in urban India and is defined on body mass index centiles rather than absolute values, because normal body mass index changes with age.

The overwhelming majority is nutritional and exogenous. The useful discriminator is height: an obese child who is tall is almost always simply overnourished, whereas an obese child who is short has an endocrine or syndromic cause such as hypothyroidism, Cushing syndrome or Prader-Willi syndrome, because those conditions impair linear growth while promoting adiposity.

5. Development: The Four Domains

Development is assessed across gross motor, fine motor and vision, hearing speech and language, and social behaviour and play.

Assessing them separately matters because the pattern of delay localises the problem. Isolated motor delay suggests a neuromuscular problem, isolated speech delay suggests hearing loss until proved otherwise, and global delay across all domains suggests an intellectual or syndromic cause.

Development proceeds in a fixed order and in two consistent directions: cephalocaudal, meaning head control before sitting before walking, and proximal to distal, meaning whole-hand grasp before pincer grip.

Primitive reflexes are present at birth and disappear as cortical control develops. The Moro reflex disappears by around four months and the grasp reflex by about six.

Persistence of primitive reflexes beyond the expected age is a hard neurological sign, because it indicates that cortical inhibition has failed to develop, and it is one of the earliest indicators of cerebral palsy.

6. The Milestones

A relatively small number of milestones are examined repeatedly and are worth knowing exactly.

The social smile at six weeks is the earliest milestone with real diagnostic weight, because its absence is an early marker of visual impairment or of significant neurological problems.

Two milestones are examined more than the rest. A pincer grip appears at around a year, and a two-word sentence at around two years.

7. Delay and Red Flags

Developmental delay means failure to reach milestones at the expected age. Global developmental delay means significant delay in two or more domains.

Certain findings are red flags requiring assessment rather than reassurance.

No social smile by ten weeks. No head control by four months. Not sitting unsupported by nine months. Not walking by eighteen months. No words by eighteen months. No two-word phrases by two years.

Loss of previously acquired skills is the most serious finding of all. Regression is never normal, and it points to a neurodegenerative or metabolic disorder, or to Rett syndrome in a girl who develops normally and then loses purposeful hand use.

Hand preference before eighteen months is also abnormal, because it suggests weakness of the other side rather than early dexterity.

Speech delay requires formal hearing assessment in every case, because hearing loss is common, treatable and easily missed, and a child who cannot hear cannot learn to speak.

8. Cerebral Palsy

Cerebral palsy is a disorder of movement and posture from a non-progressive insult to the developing brain.

The word non-progressive is the defining feature. The lesion does not worsen, though its clinical manifestations change as the child grows, and progression of the underlying process indicates a different diagnosis entirely.

Causes are antenatal in the majority, including congenital infection and malformation, with intrapartum asphyxia accounting for a smaller proportion than is commonly assumed. Prematurity is a major risk factor, and periventricular leukomalacia in a preterm infant characteristically produces spastic diplegia because the fibres to the legs run closest to the ventricles.

Types are spastic, which is commonest, dyskinetic, ataxic and mixed. Spastic disease is further divided into hemiplegia, diplegia and quadriplegia.

Presentation is with delayed motor milestones, abnormal tone, persistent primitive reflexes and asymmetry. Associated problems are frequently more disabling than the motor disorder itself: epilepsy, intellectual disability, visual and hearing impairment, feeding difficulty and hip dislocation.

Management is multidisciplinary, aimed at function rather than cure, with physiotherapy, orthoses, botulinum toxin for focal spasticity and orthopaedic surgery.

9. Autism, Attention Deficit and Puberty

Autism spectrum disorder is characterised by persistent deficits in social communication and interaction, together with restricted and repetitive patterns of behaviour, with onset in early development.

The two domains must both be present, and the diagnosis is clinical. Early signs are absent joint attention, absent pointing to share interest, lack of response to name, and absent pretend play.

Attention deficit hyperactivity disorder requires inattention, hyperactivity and impulsivity that are developmentally inappropriate, present in more than one setting, and causing impairment. The requirement for more than one setting matters, because behaviour occurring only at home or only at school usually has a situational explanation.

Puberty in girls begins with breast development and in boys with testicular enlargement to a volume above four millilitres.

The order matters more than the timing, because a change out of sequence suggests a pathological androgen or oestrogen source rather than activation of the axis.

Precocious puberty is secondary sexual characteristics before eight in girls and nine in boys, and it is developed further in the Menstrual Disorders chapter. Delayed puberty is absence by thirteen in girls and fourteen in boys.

10. Worked Examples

Example 1. A 2-year-old is on the third centile for weight, the twenty-fifth for height and the fiftieth for head circumference.

The order of involvement is diagnostic. Weight is affected most, height less, and head circumference not at all, which is the classic pattern of undernutrition rather than of an endocrine or genetic cause.

The body sacrifices fat and muscle first, linear growth second and brain growth last, so this hierarchy indicates a nutritional problem of relatively recent onset. An endocrine cause would show the opposite pattern, with height affected more than weight.

Example 2. A 12-year-old boy is short with a bone age of 10, and his father reports having grown late.

The delayed bone age is the key finding, because it means his skeletal maturation is behind his chronological age and therefore that growth potential remains.

Combined with the family history, this is constitutional delay of growth and puberty. He will enter puberty late and continue growing after his peers have stopped, reaching a normal adult height. Familial short stature would show a bone age matching chronological age, with short parents and no delay.

Example 3. An 18-month-old who was walking and speaking a few words has lost both skills over three months, and now makes repetitive hand-wringing movements.

Loss of acquired skills is never normal and immediately separates this from simple developmental delay.

Regression with loss of purposeful hand use and the appearance of stereotypic hand movements in a girl of this age is characteristic of Rett syndrome. Neurodegenerative and metabolic disorders must also be considered, and urgent specialist referral with neuroimaging and metabolic investigation is required.

Summary

• Growth measures the body against time; development measures function against time.
• In growth failure, weight falters first, then length, then head circumference.
• That order reflects a hierarchy of protection, with the brain sacrificed last.
• Weight affected alone means undernutrition.
• A trend across time matters more than a single point.
• India uses World Health Organization standards to five years, then Indian Academy charts.
• A standard is prescriptive; a reference merely describes a population.
• Some centile crossing in the first two years is physiological.
• Mid-parental height contextualises a low measurement.
• Up to 10 per cent weight loss in the first week is physiological.
• Birth weight is regained by 10 to 14 days.
• Weight doubles by 5 months and triples by a year.
• Head circumference is about 35 cm at birth and 47 cm at a year.
• The anterior fontanelle closes between 9 and 18 months.
• Normal velocity below the third centile means constitutionally small.
• Abnormal velocity means pathologically short, even within the normal range.
• Proportionate short stature suggests systemic or endocrine causes.
• Disproportionate short stature suggests skeletal dysplasia or rickets.
• Bone age separates familial short stature from constitutional delay.
• Undernutrition reduces weight before height; endocrine causes reverse this.
• A short overweight child suggests endocrine disease, not malnutrition.
• Consider Turner syndrome in every short girl.
• Faltering growth asks whether intake, absorption or retention is failing.
• Observing a feed identifies the cause more often than investigation.
• Microcephaly may be primary or secondary; secondary faltered after birth.
• Macrocephaly crossing centiles with a tense fontanelle suggests hydrocephalus.
• An obese tall child is overnourished; an obese short child is endocrine.
• The four domains are gross motor, fine motor, speech, and social.
• Isolated speech delay means hearing loss until proved otherwise.
• Global delay suggests an intellectual or syndromic cause.
• Development is cephalocaudal and proximal to distal.
• Persistent primitive reflexes are a hard neurological sign.
• Social smile at six weeks; its absence is an early marker.
• Pincer grip at one year; two-word sentences at two years.
• Red flags include no words by eighteen months and no walking by eighteen months.
• Regression is never normal.
• Hand preference before eighteen months suggests contralateral weakness.
• Cerebral palsy is non-progressive; progression means another diagnosis.
• Periventricular leukomalacia causes spastic diplegia because leg fibres lie medially.
• Associated problems in cerebral palsy often exceed the motor disability.
• Autism requires both social communication deficits and restricted behaviours.
• Attention deficit disorder must be present in more than one setting.
• Puberty starts with breast budding in girls and testicular enlargement in boys.
• Sequence out of order suggests a pathological hormone source.