Baby Development Month by Month

Every baby develops at their own pace. These month-by-month guides show what to expect in physical, cognitive, and social development — along with feeding, sleep, common concerns, and activities for each age. All information is based on CDC, WHO, and AAP guidelines.

Content reviewed against published CDC, WHO, AAP guidelines

Editorial policy

Last reviewed: July 2026

1 Month Old

Your newborn is adjusting to life outside the womb. Most of their movements are reflexive, and they spend the majority of their time sleeping and eating.

2 Months Old

Your baby is becoming more alert and interactive. You may see the first real smiles and hear cooing sounds. This is also the first major vaccine visit.

3 Months Old

A social turning point. Your baby smiles intentionally, laughs for the first time, and is increasingly engaged with the world around them.

4 Months Old

A major developmental leap. Your baby is reaching for objects, rolling, and becoming much more interactive. The 4-month sleep regression may arrive.

5 Months Old

Your baby is building strength for sitting and may be rolling both ways. Everything goes in the mouth as oral exploration peaks.

6 Months Old

A milestone month. Most babies are ready to start solid foods, can sit with minimal support, and are becoming truly interactive communicators.

7 Months Old

Your baby is on the move. Crawling, pulling up, and exploring everything within reach. Baby-proofing becomes essential.

8 Months Old

Object permanence clicks. Your baby knows things exist when hidden, which drives both exploration and separation anxiety. The 8-month regression may arrive.

9 Months Old

Your baby understands more than they can say. They follow simple commands, point to things they want, and are becoming increasingly independent.

10 Months Old

Pre-walking energy. Your baby may be cruising, standing alone, or even taking first steps. Communication through gestures is blossoming.

11 Months Old

Almost a toddler. Your baby is likely cruising, may be walking, and understands far more language than they can produce.

12 Months Old

Your baby is one year old. Whether walking, cruising, or still crawling, this is a major milestone month with a comprehensive well-child visit and vaccines.

Bottom line

Every baby develops at their own pace. The month-by-month guides above show typical ranges based on CDC, WHO, and AAP guidelines. Missing a milestone doesn't necessarily mean something is wrong — but if you have concerns, your pediatrician can help.

Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.

All content follows our editorial policy and is reviewed against published clinical guidelines.

2,705 evidence-based guides6 authoritative medical sources5 medical advisory board members