Your Baby's First Year: Month-by-Month Guide
Review general month-by-month development ranges during a baby’s first year, with variability, safety notes and reasons to contact a clinician.
A baby’s first year includes rapid changes in communication, movement, learning and social interaction. This guide uses the CDC’s milestone checkpoints to help caregivers know what to observe and what to discuss at a routine visit. Milestones are conversation tools, not a scorecard or diagnosis.
What a developmental milestone means
The CDC describes milestones as things most children—75% or more—can do by a particular age. The checklists group observations into four areas: social and emotional, language and communication, cognitive, and movement and physical development. They are designed to support developmental monitoring and a conversation with a healthcare professional.
A milestone age is not a competition and the checklist is not a substitute for standardized developmental screening. Premature babies may also be assessed using corrected age during early development; your child’s clinician can explain when and how that applies.
Two-month checkpoint
At two months, the CDC checklist includes observations such as calming when spoken to or picked up, looking at a caregiver’s face, reacting to loud sounds, watching movement and holding the head up during tummy time. Caregivers can support interaction by talking, reading, responding to sounds and providing supervised awake tummy time.
Keep notes about what you see rather than trying to test the baby. A short video of a movement or sound can be helpful when describing a question at an appointment.
Four-month checkpoint
The four-month checklist looks for a broader range of social responses, sounds and controlled movement. Examples include smiling to gain attention, chuckling, making sounds in response to a caregiver, holding the head steady and bringing hands to the mouth. The exact pattern differs between babies, so look for change over time across several areas.
Six-month checkpoint
By the six-month checkpoint, the CDC includes recognizing familiar people, laughing, taking turns making sounds, reaching for a wanted toy, rolling from tummy to back and leaning on hands while sitting. Questions about introducing foods, allergies or feeding readiness belong with a pediatric professional because individual health and development matter.
Nine-month checkpoint
The nine-month checklist includes looking when called by name, showing different facial expressions, reacting when a caregiver leaves, making repeated sounds, looking for an object that dropped out of sight, getting to a sitting position and moving an item from one hand to the other. Some children move around without conventional crawling, so describe the movement you observe rather than comparing styles.
Twelve-month checkpoint
At twelve months, examples on the CDC checklist include playing simple social games, waving, calling a parent by a special name, understanding “no,” putting an object into a container, pulling up to stand and walking while holding furniture. Independent walking is not the only measure of development at the first birthday.
How to prepare for a well-child visit
- Note new skills, communication and movement since the last visit.
- Write down any skill the child stopped doing, as loss of a skill deserves prompt discussion.
- List questions about sleep, feeding, hearing, vision, movement or interaction.
- Bring the child’s age and, if relevant, gestational age at birth so the clinician has context.
- Ask whether a formal developmental screening is due; monitoring and screening are related but different.
Use age calculations carefully
Our Baby Age Calculator reports chronological age in months, weeks and days and can show corrected age when the required birth information is entered. It does not evaluate a milestone or tell you whether development is typical. Pair the age result with the current CDC checklist and a clinician’s assessment.
When to ask for help
Contact your child’s healthcare professional whenever you have a concern, when a checklist item is not present by its checkpoint, or when a child loses a skill previously shown. The CDC advises caregivers not to wait when concerned. A professional can review the full picture, perform screening when appropriate and explain the next step.
Key takeaways
- Use milestone checklists to observe and prepare questions, not to diagnose.
- Look across communication, social interaction, learning and movement.
- Track changes over time and share specific observations with the child’s clinician.
- Use corrected age only with appropriate birth information and clinical guidance.
- Act early when concerned or when a skill is lost.
Sources & scope
Milestones describe common patterns, not a deadline or diagnosis; caregivers should use their own clinician for individual concerns.
Sources accessed: August 8, 2026 · Links are provided for verification and further reading.