Early childhood, which typically spans from birth to 8 years of age, is characterized by rapid growth and development. Close monitoring during this period ensures children are meeting age-specific milestones and that deviations from expected developmental trajectories are quickly identified. Developmental delays affect ∼ 15% of children and can impact more than one domain (i.e., physical, language, cognitive, and social and emotional development); early identification and treatment can improve outcomes. Developmental milestones are an important component used to track a child's progress over time and provide a framework by establishing a set of skills or behaviors that most children are expected to achieve by a certain age. A child's development should be assessed at every well-child visit and whenever there is a concern for abnormal development. For children who are not meeting their milestones, an evaluation of abnormal pediatric development and relevant referrals are indicated.
Overview of normal development
Normal development in childhood involves the evolution and resolution of primitive reflexes, and the sequential development of motor, language, cognitive and social skills (tracked using developmental milestones). Throughout childhood, various behaviors (e.g., stranger anxiety, magical thinking, imaginary companions) may also be temporarily observed and are part of normal development; caregivers should be reassured that these behaviors will resolve as children age.
General principles 
- Primitive reflexes are transient reflexes that manifest during infancy and disappear when subcortical motor inhibitory pathways develop (usually within the 1st year of life).
- Evaluation of primitive reflexes is an essential part of the .
- Abnormal primitive reflexes are those that are absent, asymmetric, and/or persist past the expected age range.
|Overview of primitive reflexes |
|Reflex||Description||Typical age range ||Clinical significance|
|Glabellar tap sign || || || |
|Snout reflex || |
|Rooting reflex|| || || |
|Sucking reflex|| |
|Asymmetrical tonic neck reflex (ATNR)|| || |
|Moro reflex (Star lex)|| |
|Palmar grasp reflex|| || |
|Plantar grasp reflex|| || || |
Extensor plantar reflex (Babski reflex)
| || || |
|Landau reflex|| |
|Parachute reflex|| || |
|Truncal incurvation reflex (G nt reflex) || || |
|Stepping reflex || |
General principles 
- Develop tal milestones are the expected abilities that most children can do by a defined age and are:
- Abnormal development occurs when children fail to attain developmental milestone(s) by the expected age and/or in the expected order.
- ∼15% of children have developmental delay. 
- Common etiologies include:
- Neurologic injury
- Parental neglect
Developmental domains 
- Gross motor development: the development of movements (e.g., sitting up, walking) that require the use of large muscle groups
- Fine motor development: the development of precise movements using hands and smaller muscles (e.g., picking up a small object)
Language development: the development of communication through either spoken or signed language
- Receptive language: the ability to understand and process language
- Expressive language: the ability to formulate language
- Cognitive development: the development of reasoning and problem-solving skills
- Social and emotional development: the development of self-regulation and attachment and interaction with others
Age-specific developmental milestones
- In 2022, the CDC recommended using the 75th percentile rather than the 50th percentile for developmental surveillance; the following tables reflect this change. 
- If a child is not meeting milestones, conduct an immediate . 
A wait-and-see approach is no longer recommended for potential developmental delay. 
Developmental milestones in infants 
|Overview of developmental milestones in infants |
|Motor development||Speech development||Cognitive and social development|
|2 months|| || || |
| || || |
|6 months|| || |
|9 months|| || |
|12 months|| || || |
Children, including twin siblings, develop at different speeds and one child's milestones should not be used to evaluate another child's development.
Developmental milestones in childhood 
|Overview of developmental milestones in children 1–5 years |
|Age||Motor development||Speech development||Cognitive and social development|
|15 months|| || || |
|18 months|| || || |
|2 years|| || || |
|2.5 years (30 months)|| || || |
|3 years|| || || |
|4 years|| || || |
|5 years|| || || |
Common developmental behaviors
Certain temporary pediatric behaviors are considered normal parts of cognitive, imaginative, and creative development, e.g.:
Stranger anxiety: when an infant is fearful of unknown individuals
- Expected ages: 6 months–3 years 
- Clinical features: crying and/or clinging to a known caregiver when around strangers
Separation anxiety: when an infant or young child is afraid of being separated from their caregiver
- Expected ages: peaks between 9 and 18 months and resolves by 3 years of age 
- Clinical features
- Crying and/or clinging to a caregiver if the caregiver tries to leave
- Continued crying after a caregiver has left
- Pretend play: when a young child imitates adult activities and/or interactions 
Magical thinking: when thoughts are believed to affect change and nonrelated events are causally linked 
Expected ages: ∼4–5 years
- Decreases with age
- Some persistence into adulthood may occur. 
- Assuming their actions cause unrelated events
- Attributing emotions to an inanimate object
- Believing that wishing for something causes it to come true
- Expected ages: ∼4–5 years
Imaginary companion: when a fictitious human, animal, or object is treated as if it were alive 
- Expected ages: Preschool and young school-aged children 
- Benefits are similar to those of pretend play. 
Common reactions to specific life events
Arrival of a sibling 
The arrival of a sibling can pose significant stress to a child, who may react with negative emotions (e.g., jealousy, anxiety, resentment, anger) and changes in behavior. Further typical reactions include:
- Bedwetting in a toilet-trained child
- Finger or thumb sucking
- Demanding help with eating
- Wanting to drink from baby's bottle and/or wanting to breastfeed
- Speaking like a baby
- Changes in sleeping pattern
- Violent behavior towards the sibling and/or caregivers (e.g., hitting, biting)
- Regression (psychiatry)
Counsel caregivers about the older child's possible reactions and advise them to:
- Avoid other major changes at the same time as the anticipated arrival (e.g., moving houses, starting new kindergarten).
- Organize caregiving support from other family and friends.
- Spend alone time with the older child after the baby's arrival.
- Encourage the older child to take part in the caretaking of their sibling and praise them for doing so.
- Acknowledge the older child's negative emotions and reinforce their importance and sense of security.
Understanding of death 
- A child's understanding of death depends strongly on their developmental age, personal experiences, and parental communication about death (including parents' spiritual and religious beliefs).
- An adult understanding of death involves the comprehension of the following concepts:
Concepts of death at different ages
- Infants and toddlers (0–2 years): no understanding of death
- Preschoolers (3–5 years):
- School-age children (6–12 years):
- Adolescents (13–18 years): typically have an adult understanding of death
- Early identification and treatment of developmental delay improve outcomes.
- In children < 2 years old who were born prematurely, the chronological age must be adjusted for gestational age. 
- Developmental surveillance should be performed at every and includes: 
Developmental screening uses validated tools and should be used at set well-child visits or if there are concerns. 
- Parent-completed tools can be used for initial screening.
- If abnormal, directly administered tools are used for further evaluation.
Types of abnormal development 
Developmental delay: Milestones occur in the expected order but not by the expected ages.
- 1 domain affected: isolated developmental delay
- ≥ 2 domains affected: 
- Developmental dissociation
- Developmental deviation: Developmental milestones within a given domain are not achieved in the expected order.
- Developmental regression: the loss of previously acquired skills
Evaluation of abnormal pediatric development 
- Confirm developmental abnormalities are present using validated developmental screening (if not already performed).
- Obtain a full medical history (e.g., in utero, birth, past medical history, and family history).
- Evaluate for abnormal physical findings. 
- Perform a detailed neurological examination.
- Rule out and .
- Screen and test for common underlying etiologies.
- For children with suspected global developmental delay, see also “Diagnostics of global developmental delay.”
Management of abnormal pediatric development 
- Identify and treat underlying medical comorbidities (e.g., hearing loss).
- Refer to a specialist based on clinical features and local availability. 
- Involve relevant therapy services, as needed.
- Ensure regular follow-up.
- See also “Neurodevelopmental disorders.”
- Proactively discuss with caregivers ways of encouraging normal development, e.g.:
- Initiate supervised tummy time early. 
- Increase gradually based on the infant's interest level.
- The target is 30 minutes spread out over the day.
- Talk to and with the child. 
- Describe everyday activities to the child.
- Sing nursery rhymes.
- Promote early exposure to books.
- Point to and name everyday objects.
- Actively play with the child, e.g.: 
- Interact with reciprocal games like pat-a-cake, peek-a-boo, Simon says.
- Make different faces with the child.
- Demonstrate how to use age-appropriate toys or household items.
- Introduce different objects of different textures, sizes, and colors.
- Engage in role-playing.
- Initiate supervised tummy time early. 
- Advise on adequate sleep, nutrition, and physical exercise to support development (see “Anticipatory guidance for children”).
- Ensure caregivers know the expected developmental milestones for their child's age.
- Advise caregivers to consult a healthcare professional early if they have development concerns, rather than waiting to see if the child will catch up. 
Reading, talking, singing, and playing with infants promotes normal early pediatric development.