Developmental Milestones: CDC Guidelines, Red Flags, Early Intervention, and ASD Screening
Exhaustive guide to CDC developmental milestones from 2 months to 5 years, including red flags for developmental delay, early intervention services, and autism spectrum disorder screening tools and pathways.
This content is for informational purposes only. Always consult a healthcare professional.
Introduction
Developmental monitoring (surveillance) and screening are essential components of pediatric well-child care. The CDC’s “Learn the Signs. Act Early.” program provides evidence-based milestones for parents and providers. Early identification of developmental delays enables early intervention, which improves long-term outcomes.
CDC Milestones (2 Months - 5 Years)
[See comprehensive CDC milestone tables in 01-growth-development.md]
Red Flags for Developmental Delay
By Age
Age
Social/Emotional
Language
Cognitive
Motor
2 months
No social smile
Not responding to loud sounds
Not tracking objects
Not holding head up on tummy
4 months
No smiling spontaneously
No cooing
Not reaching for objects
Poor head control; not pushing up
6 months
No response to people
No babbling
Not bringing things to mouth
Stiff/floppy; not rolling
9 months
No fear of strangers
No babbling with consonants
Not searching for hidden object
Not sitting without support
12 months
No waving/pointing
No single words
Not imitating gestures
Not pulling to stand
15 months
No pointing
<3 words
Not learning function of objects
Not walking
18 months
Not showing interest in others
<10-15 words; no 2-word phrases
Not imitating
Not walking
24 months
No parallel play; no pretend
<50 words; no 2-word combinations
Cannot follow 2-step commands
Not running
30 months
No pretend play with others
Not understood by caregivers
Not scribbling
Not jumping
3 years
Not playing with others
Not speaking in sentences
Cannot complete simple puzzles
Frequent falling; not climbing
4 years
No imaginative play
Not understood by strangers
Cannot draw simple shapes
Cannot hop on one foot
5 years
No interest in peers
Cannot tell a story; not speaking clearly
Cannot copy shapes
Not standing on one foot 10 sec
Absolute Red Flags at Any Age
Red Flag
Possible Concern
Loss of previously acquired skills (regression)
Autism, Rett syndrome, metabolic disorders, neurodegeneration
Hand dominance before 18 months
Contralateral hemiparesis (cerebral palsy)
Persistent fisting beyond 4 months
Upper motor neuron lesion
Asymmetric crawl (crawling with one side dragging)
Hemiparesis
Toe walking beyond 2-3 years (persistent)
Cerebral palsy, autism, idiopathic
Inability to sit by 9 months
Cerebral palsy, global delay
No words by 18 months
Language disorder, autism, hearing loss
No phrases by 24 months
Language disorder, autism, intellectual disability
Any loss of language or social skills
Autism, Landau-Kleffner syndrome, metabolic
Screening Tools
Standardized Screening by Age
Age
Screening Domain
Recommended Tool
9 months
General development
Ages and Stages Questionnaire (ASQ-3)
18 months
General development + Autism
ASQ-3 + Modified Checklist for Autism in Toddlers (M-CHAT-R/F)
24 months
General development + Autism
ASQ-3 + M-CHAT-R/F (or autism-specific)
30 months
General development
ASQ-3
3, 4, 5 years
Development and School Readiness
ASQ-3, Parent’s Evaluation of Developmental Status (PEDS)
Commonly Used Screening Instruments
Tool
Age Range
Domains
Time
Sensitivity
Specificity
ASQ-3
1-66 months
Communication, gross motor, fine motor, problem solving, personal-social
10-15 min
70-90%
80-90%
M-CHAT-R/F
16-30 months
Autism risk
5-10 min
85%
95%
PEDS
0-8 years
General development (parent concerns)
5 min
70-80%
70-80%
SWYC (Survey of Wellbeing of Young Children)
0-5 years
Development, behavior, autism, family risk
10-15 min
70-80%
70-80%
Autism Spectrum Disorder (ASD) Screening
M-CHAT-R/F (Modified Checklist for Autism in Toddlers, Revised/Follow-up)
Score
Risk Category
Action
0-2
Low risk
No further action (routine screening at next well visit)
3-7
Medium risk
Administer Follow-up (F) interview; if still positive >2, refer for evaluation
8-20
High risk
Bypass Follow-up; refer immediately for diagnostic evaluation + Early Intervention
Red Flags for ASD (CDC)
Age
Red Flag
Any
No big smiles or warm expressions by 6 months
9 months
No back-and-forth sharing of sounds, smiles, facial expressions
12 months
No babbling; no pointing; no responding to name; no gestures (waving)
16 months
No words
24 months
No meaningful 2-word phrases (not just imitating/evaluating)
Any age
Loss of language, social skills, or any skills (regression)
Other ASD Screening Tools
Tool
Age
Description
STAT (Screening Tool for Autism in Toddlers)
24-36 months
Interactive; 20 min; requires training
CARS (Childhood Autism Rating Scale)
2+ years
Observational; 20-30 min; severity rating
ADOS-2 (Autism Diagnostic Observation Schedule)
12 months +
Gold standard diagnostic observation; requires certification
Early Intervention (EI) Services
Eligibility
Age
System
Eligibility Criteria
0-3 years
Early Intervention (Part C of IDEA)
Established condition (genetic syndrome, hearing loss) OR developmental delay of 25-30% in one or more domains
3-5 years
Preschool Special Education (Part B, Section 619)
Classified under one of 13 disability categories
5-21 years
School-age special education (Part B)
Individualized Education Program (IEP)
Services Provided by Early Intervention
Service
Description
Developmental therapy
Play-based learning to address delays
Speech-language therapy
Communication, oral motor, feeding
Occupational therapy
Fine motor, sensory processing, self-care, feeding
Physical therapy
Gross motor, mobility, balance
Behavioral therapy
ABA for autism-related behaviors
Social work
Family support, resource navigation
Nutrition counseling
Feeding difficulties, growth
Audiology
Hearing assessment and management
Vision services
Visual impairment support
Referral Process
Step
Action
1
Screening positive: discuss with family (provide in writing)
2
State-specific Early Intervention referral (phone, online, or written)
3
EI has 45 days from referral to complete evaluation (federal mandate)
4
If eligible: develop Individualized Family Service Plan (IFSP) within 45 days
5
Services begin; progress reviewed every 6 months
6
Transition at age 3 to preschool special education
Common Developmental Disorders
Disorder
Prevalence
Key Features
Screening Approach
Autism spectrum disorder
1 in 36 (CDC 2023)
Social communication deficits, restricted/repetitive behaviors, sensory differences
M-CHAT-R/F at 18 and 24 months
Attention-deficit/hyperactivity disorder (ADHD)
5-10%
Inattention, hyperactivity, impulsivity
Vanderbilt Rating Scales (parent and teacher)
Developmental language disorder
7-10%
Difficulty understanding or using language
ASQ-3, PLS-5
Intellectual disability
1-3%
IQ <70, adaptive behavior deficits
Developmental assessment
Cerebral palsy
1-2 per 1,000
Motor impairment from non-progressive brain injury
Neurologic exam; tone, reflexes, motor milestones
Global developmental delay
1-3%
Delay in 2+ domains
ASQ-3, comprehensive evaluation
Specific learning disorder
5-15%
Difficulty reading (dyslexia), math (dyscalculia), writing
Academic testing after age 6-7
Medical Evaluation for Developmental Delay
Component
What to Assess
History
Prenatal, perinatal, postnatal; regression; seizures; family history; social history; prior evaluations