DOMAIN 1 PART A

Domain 1 — Growth, Development, Puberty & General Pediatrics

Part A — Normal Growth and Childhood

1.1 Physiological growth of the child and its assessment

1. Basic concept

Growth is the quantitative increase in body size from birth to adulthood. It reflects the interaction of:

  • Genetic potential

  • Nutrition

  • Hormonal factors

  • Chronic disease

  • Psychosocial environment

  • Prenatal and placental factors

The most important rule is:

Growth must be assessed longitudinally. Serial measurements and growth velocity are more important than one isolated percentile.



2. Main growth parameters

Assess:

  • Weight

  • Length / height

  • Head circumference

  • B M I or weight-for-length

  • Growth velocity

  • Body proportions

  • Pubertal stage

  • Genetic target height

Weight

Normal term birth weight: approximately 3 to 3.5 kg

Physiological neonatal weight loss:

  • Up to about 7 to 10 percent

  • Usually regained by 10 to 14 days

Expected weight pattern:

  • Doubles by 4 to 6 months

  • Triples by 1 year

  • Approximately quadruples by 2 years



3. Length and height

Typical values:

Age

Approximate length/height

Birth

50 cm

1 year

75 cm

2 years

85 to 90 cm

4 years

100 cm

Normal growth velocity

  • First year: approximately 25 cm/year

  • Second year: 10 to 12 cm/year

  • Prepubertal childhood: about 5 to 7 cm/year

  • Pubertal spurt: roughly 8 to 12 cm/year

Supine length is generally measured below 2 years.
Standing height is used thereafter.



4. Head circumference

Normal term newborn: approximately 35 cm

Head circumference grows rapidly during the first 2 years because of rapid brain growth.

Measure particularly in infants and toddlers.

Abnormalities:

  • Small head circumference → microcephaly

  • Rapidly increasing head circumference → consider hydrocephalus

  • Always interpret using age- and sex-specific charts



5. Growth charts

Plot measurements on age- and sex-specific charts.

Important variables:

  • Weight-for-age

  • Height-for-age

  • Weight-for-length in infants

  • B M I-for-age in older children

  • Head circumference-for-age

Values are expressed as percentiles or Z-scores.

Short stature is generally:

  • Height below approximately minus 2 S D

  • Roughly below the 2nd to 3rd percentile

However, being short is not automatically pathological.

Red flags

  • Downward crossing of two major percentile channels

  • Reduced height velocity

  • Height clearly inconsistent with parental target

  • Disproportionate body habitus

  • Delayed or abnormal puberty

  • Associated systemic symptoms

  • Very low or very high B M I



6. Mid-parental target height

Boy

Father's height + mother's height + 13 cm, divided by 2

Girl

Father's height + mother's height minus 13 cm, divided by 2

Expected adult height is usually approximately within plus or minus 8.5 cm of target height.



7. Bone age

Usually assessed by an X-ray of the left hand and wrist.

Useful in growth disorders.

Familial short stature

  • Short child

  • Short parents

  • Normal growth velocity

  • Bone age approximately equals chronological age

  • Adult height remains short

Constitutional delay of growth and puberty

  • Short during childhood

  • Normal growth velocity

  • Delayed bone age

  • Delayed puberty

  • Often family history of late puberty

  • Final adult height usually appropriate

Endocrine disease

Often:

  • Reduced linear growth

  • Delayed bone age

  • Weight relatively preserved or increased

Chronic/systemic/nutritional disease

Often:

  • Poor weight gain occurs before or together with reduced height gain



8. Hormonal regulation of growth

Fetal growth

Mainly influenced by:

  • Genetics

  • Maternal nutrition

  • Placental function

  • Insulin and growth factors

Growth hormone is relatively less important prenatally.

Infancy

Nutrition is especially important.

Childhood

Main regulators:

  • Growth hormone

  • I G F 1

  • Thyroid hormones

Puberty

Growth acceleration occurs through:

  • Growth hormone

  • I G F 1

  • Sex steroids

Estrogen causes final epiphyseal closure in both girls and boys.

In boys, testosterone is partly converted to estrogen by aromatase.

Memorize:
G H and I G F 1 = growth
Estrogen = growth-plate closure



9. Normal puberty and growth spurt

Girls

First pubertal sign:
Breast development

Typical order:

Thelarche → growth spurt → pubic hair progression → menarche

Peak height velocity occurs before menarche.

Some additional growth continues after menarche.

Boys

First pubertal sign:
Testicular enlargement

Pubertal growth spurt:

  • Occurs later than in girls

  • Usually reaches a higher peak growth velocity



28.1 Characteristics of childhood, division, specifics

1. Main periods of childhood

A practical division:

Neonatal period

Birth to 28 days

Early neonatal:

  • First 7 days

Late neonatal:

  • 8 to 28 days

Infancy

Approximately 1 month to 1 year

Toddler period

Approximately 1 to 3 years

Preschool age

Approximately 3 to 6 years

School age

Approximately 6 years to puberty

Adolescence

Puberty through completion of physical and psychosocial maturation



2. Why children are not small adults

Children differ anatomically and physiologically from adults.

These differences change:

  • Normal vital signs

  • Fluid requirements

  • Drug dosing

  • Response to illness

  • Airway management

  • Thermoregulation

  • Metabolism



3. Body composition and water

Infants have a higher total body water percentage.

Approximate:

  • Preterm newborn: around 80 to 85 percent

  • Term newborn: around 75 percent

  • Adult: around 60 percent

Infants also have proportionally more extracellular fluid.

Consequences:

  • Faster dehydration

  • Greater sensitivity to fluid losses

  • Electrolyte disturbances develop more quickly



4. Metabolism

Children, especially infants, have:

  • Higher metabolic rate per kilogram

  • Higher oxygen consumption per kilogram

  • Higher caloric requirements per kilogram

  • Smaller energy reserves

Therefore they can deteriorate rapidly during illness, fasting or respiratory compromise.



5. Respiratory characteristics

Children have:

  • Smaller airway diameter

  • Relatively large tongue

  • Higher and more anterior larynx in younger children

  • More compliant chest wall

  • Higher respiratory rate

Because airway radius is small, even mild edema can greatly increase airway resistance.

This explains why conditions such as croup or airway inflammation may cause major obstruction.



6. Cardiovascular characteristics

Compared with adults, younger children normally have:

  • Higher heart rate

  • Lower blood pressure

  • Cardiac output more dependent on heart rate

Normal values vary strongly with age.

Tachycardia is often an early sign of deterioration.

Hypotension may be a late sign of pediatric shock.



7. Renal characteristics

In newborns and young infants:

  • G F R is lower

  • Tubular function is immature

  • Concentrating ability is reduced

  • Sodium and water handling are less efficient

Consequences:

  • Increased risk of dehydration and electrolyte disturbance

  • Drug elimination may differ from adults

  • Fluid therapy must be carefully calculated



8. Thermoregulation

Infants have:

  • Large surface-area-to-mass ratio

  • Thin skin

  • Less insulation

  • Limited ability to generate heat by shivering

Therefore they lose heat easily.

Newborns rely significantly on non-shivering thermogenesis via brown adipose tissue.



9. Body proportions

At birth:

  • Head is proportionally large

  • Limbs are relatively short

  • Trunk contributes more to total length

With growth:

  • Limbs lengthen proportionally

  • Head becomes relatively smaller

  • Adult body proportions gradually develop

Body proportions are useful when assessing disorders such as skeletal dysplasias.



10. Immune system

The neonatal and infant immune system is immature.

Important features:

  • Maternal I g G crosses the placenta

  • Breast milk provides especially secretory I g A

  • Passive maternal antibodies decline during infancy

  • Adaptive immunity gradually matures

Young infants are therefore more vulnerable to certain severe infections.



11. Pediatric pharmacology

Drug therapy cannot simply be calculated as a proportion of the adult dose.

Differences include:

  • Absorption

  • Distribution

  • Body water and fat composition

  • Hepatic metabolism

  • Renal elimination

  • Protein binding

Most drugs are therefore prescribed according to:

mg/kg, sometimes mg/m²

Always respect:

  • Maximum adult dose

  • Age restrictions

  • Renal/hepatic function



12. Important age-related clinical principle

Normal values change with age.

This applies to:

  • Heart rate

  • Respiratory rate

  • Blood pressure

  • Laboratory reference ranges

  • Drug doses

  • Developmental abilities

  • Nutritional requirements

A value that is normal for an infant may be abnormal for an adolescent.



High-yield oral exam summary

Normal growth

Birth: 3 to 3.5 kg, 50 cm, head circumference 35 cm.

Weight:
Double by 4 to 6 months.
Triple by 1 year.

Height:
First year plus 25 cm.
Second year plus 10 to 12 cm.
Childhood about 5 to 7 cm/year.

Growth assessment:
Serial measurements, growth velocity, percentiles, B M I, head circumference, body proportions, parental target height, puberty and bone age.

Bone age: left hand/wrist.

Familial short stature: normal velocity, normal bone age.
Constitutional delay: normal velocity, delayed bone age.
Endocrine disease: height affected more than weight.
Systemic/nutritional disease: weight often affected first.

Characteristics of childhood

Children have:

  • More total body water

  • Faster metabolism

  • Higher oxygen demand

  • Higher heart and respiratory rates

  • Lower blood pressure

  • Smaller airways

  • Immature renal function

  • Greater heat loss

  • Age-dependent drug handling

Three facts worth memorizing

Serial growth matters more than a single percentile.
Peak female height velocity occurs before menarche.
Estrogen closes the growth plates in both sexes.