• Clinical science

Child development and milestones


Growth charts and developmental milestones are among the most important tools of pediatric screening and monitoring. Growth charts are used to assess height and weight for age, while developmental milestones define the physical, intellectual, and behavioral skills a child with normal development is expected to have acquired by a certain age. Child growth and development are assessed during routine well-child visits at regular intervals. Children whose growth and weight are far below or above average and those who do not meet the developmental milestones for their age group should be evaluated for underlying diseases and receive treatment accordingly. Failure to thrive (FTT) in infants is a condition in which an infant's growth and weight-gain are far below average, the most common cause of which is inappropriate feeding practices. Global developmental delay is defined as the significant developmental failure in two or more domains in children under 5 years of age. The regression of previously achieved milestones may also be a sign of global developmental delay. The persistence of primitive reflexes indicates impaired brain development.

Primitive reflexes

Reflex Description Age of resolution Clinical significance
Moro reflex
  • 3–6 months
Rooting reflex
  • Stroking the cheek elicits turning of the head towards the stimulus and opening of the mouth.
  • 4 months
  • Unilateral absence indicates peripheral injury
  • Bilateral absence or premature resolution
Sucking reflex
  • Touching the roof of the mouth elicits a sucking motion.
Palmar grasp
  • Stimulation of the palm elicits a grasping motion.
  • 3–6 months
Plantar grasp
  • 3 months

Plantar reflex

  • Stroking the sole of the foot from heel to toe elicits dorsiflexion of the foot with concomitant extension of the big toe and fanning of the other toes.
  • 12 months
Stepping reflex
  • Holding the infant upright with feet on the examination table elicits a stepping motion with alternating flexion and extension of the legs.
  • 2 months
Galant reflex
  • Holding the infant in the prone position and stroking it on one side of the paravertebral region elicits flexion of the lower back and hip towards the stimulus.
  • 2–6 months
Asymmetrical tonic neck reflex (ATNR)
  • Turning the head to one side elicits extension of the arm and leg on the side the head is facing and flexion of the contralateral arm and leg (fencing posture).
  • 3–4 months
  • The ATNR aids in the development of hand-eye coordination.

Glabellar tap sign

  • Tapping the glabella elicits blinking.
  • 4–6 months
Landau reflex
  • 24 months
Snout reflex
  • Tapping or applying light pressure to closed lips elicits puckering.
  • 4 months

Plantar grasp and plantar reflex are two different types of primitive reflexes!


Developmental milestones

Developmental milestones in infancy [10][11][12]

Age Gross motor Fine motor Language Social/Cognitive
2 months
  • Raises head and chest when prone
  • Follows objects past midline
  • Coos
  • Smiles back (social smile)
  • Recognizes parents

4 months

  • Holds head straight
  • Rolls over front to back
  • Props himself/herself up on wrists in prone position
  • Holds and shakes rattle
  • Laughs
  • Makes consonant sounds
  • Localizes sound
6 months
  • Sits without support
  • Rolls over back to the front
  • Grabs and transfers objects from one hand to the other
  • Raking grasp
  • Babbles
  • Develops stranger anxiety (6–9 months)
  • Develops object permanence (6–9 months)
9 months
  • Crawls
  • Stands when holding on to something
  • Pincer grasps (9-12 months)
  • Says “ma-ma”, “da-da
  • Orients to name
  • Imitates actions
  • Has separation anxiety
12 months
  • Starts to walk
  • Can throw objects
  • Points at objects
  • Knows 1–5 words
  • Follows simple commands

Developmental milestones in childhood [10][11]

Age Gross motor Fine motor Language Social/Cognitive
1.5 years
  • Starts to run
  • Stacks up to 4 blocks
  • Uses spoon and cup
  • Knows 10–50 words
  • Plays pretend
2 years
  • Walks up and downstairs, stepping with both feet on each step
  • Kicks ball
  • Jumps
  • Stacks up to 6 blocks (number of blocks = age in years x 3)
  • Draws a line
  • Knows ≥ 50 words
  • Uses sentences of up to 2 words
  • Engages in parallel play (2–3 years)
  • Moves away and comes back to the parent
  • Follows 2-step commands
  • Removes clothes
3 years
  • Alternates feet when walking up and down the stairs
  • Pedals a tricycle
  • Stacks up to 9 blocks
  • Copies a circle
  • Mostly intelligible speech
  • Knows ≥ 300 words, understands > 1000 words
  • Uses sentences of up to 3 words
  • Understands gender difference
  • Brushes teeth and grooms self
  • Has bladder and bowel control (however, bed-wetting until 5 years of age is considered normal )
  • Plays away from parents
4 years
  • Hops on one foot
  • Catches and throws ball overhand
  • Copies a square
  • Tells complex stories
  • Can identify some colors and numbers
  • Plays cooperatively
  • May have imaginary friends
5 years
  • Skips
  • Walks backwards
  • Copies a triangle
  • Can tie shoelaces
  • Can write some letters
  • Speaks fluently
  • Counts 10 or more things
  • Uses sentences of up to 5 words
  • Learns how to read
  • Understands directions (left and right)
  • Plays dress up

Chronologic age must be adjusted for gestational age for premature infants below 2 years old!

The definition of developmental delay varies depending on the state but as a general rule, developmental delay should be suspected when the child's age is > 25% of the mean age at which a particular milestone is attained or > 1.5 standard deviations on a standardized developmental screening test.

Twins, like all other children, develop at different speeds and each twin should be evaluated separately for any delays in obtaining milestones.


Normal growth in infants and young children

Growth charts are used to calculate a child's growth percentile by plotting the child's weight and height/length on standardized graphs. Height is usually measured standing up, whereas length is measured while the child is lying down.

According to the Rule of Fives, normal growth rates in children can be approximated by multiples of five: birth–1 year (50–75 cm, 25 cm/year), 1–4 years (75–100 cm, 10 cm/year), 4–8 years (100–125 cm, 5 cm/year), 8–12 years (125–150 cm, 5 cm/year).


Failure to thrive


  • Inadequate growth of a child for their age
  • Seen in up to 10% of children in the United States (most < 18 months of age)
  • Anthropometric criteria of FTT
    • Weight-for-age: < 5th percentile
    • Length-for-age: < 5th percentile
    • Body mass index-for-age: < 5th percentile
    • Deceleration of weight velocity that crosses 2 major lines on the growth chart


Clinical features



  • Treatment of the underlying cause
  • Counseling parents on appropriate child nutrition
  • Formula supplementation for infants and nutritional supplementation for toddlers
  • Close follow-up and monitoring of the child's growth


Well-child examination

Children with behavioral abnormalities should be tested for hearing loss.


Global developmental delay


Intellectual disability

References: [33][34][31]

Specific learning disorder

  • Definition
    • A neurodevelopmental disorder that occurs due to a combination of genetic, epigenetic, and environmental factors and results in difficulties learning and applying specific academic skills
    • Features should be present for more than 6 months despite academic interventions to address these problems.
  • Prevalence: 5–15% in the school-age population [33]
  • Clinical features
    • Inability to acquire age-appropriate academic skills, such as reading (most common), spelling, writing, operations with numbers,or mathematical reasoning
    • General cognitive abilities (e.g., reasoning, abstract thinking) are normal (in contrast to intellectual disability)
  • Management
    • Academic support (e.g., individualized learning programs)
    • Regular school psychology consultations
    • Individual or family psychotherapy
    • Extracurricular activities to improve academic and social inclusion

References: [33]