Baby Milestones by Month — Observation Journal

The little guide · By Dr. Baby

Baby milestones by month: use a reference, not a race

CDC milestone lists describe skills most children can do by an age. This page highlights a small selection at four, six and nine months; it is not a complete checklist or developmental screening tool. Use the official CDC checklists for the full age-specific lists, and share concerns with your pediatrician.

When do babies start laughing?

The CDC distinguishes a small chuckle on its four-month checklist from laughing on its six-month checklist. You can note the date and context of sounds you notice without treating the observation as a test.

When do babies roll over?

The CDC six-month checklist includes rolling from tummy to back. Rolling in the opposite direction is a different movement; do not assume that one entry describes both. Record the direction when you write an observation.

When do babies sit up?

The six-month CDC list includes leaning on hands for sitting support. By nine months, the list includes sitting without support and getting into a sitting position. These are distinct skills, which is why a note can be more useful than a single “sits” checkbox.

When do babies crawl?

Crawling styles and timing vary, and some babies skip hands-and-knees crawling. The AAP explains that skipping crawling does not by itself predict later reading problems. Bring concerns about movement, asymmetry, lost skills or development to your pediatrician rather than relying on a single milestone.

Selected milestones to observe

By 4 months

• A little chuckle: A small chuckle when you try to make your baby laugh.
• Turning toward your voice: Turning the head in response to your voice.

Read the complete CDC 4-month checklist ↗

By 6 months

• A fuller laugh: Laughing during interaction.
• Tummy-to-back rolling: Rolling from the tummy onto the back.
• Supported sitting: Leaning on hands while sitting.

Read the complete CDC 6-month checklist ↗

By 9 months

• Sitting independently: Sitting without support.
• Getting into sitting: Moving into a sitting position.

Read the complete CDC 9-month checklist ↗

Crawling reference: AAP · Crawling and later development