Baby development month by month, from birth to 12 months
The first year is the fastest stretch of growth your child will ever have. Here is what each stage looks like, and how to play along with it.
Updated October 13, 2026 · sources checked October 13, 2026
In short
In the first year, babies move from lifting their head on their tummy (around 2 months) to rolling (by 6 months), sitting, pulling to stand and walking with support (by 12 months). WHO data show wide normal windows: sitting alone from 3.8 to 9.2 months, walking alone from 8.2 to 17.6 months. Daily floor play, talking and reading feed every stage.
Two references, two jobs
Two kinds of data describe how babies develop, and they answer different questions:
- The CDC milestone checklists say what most babies (at least 75%) do by each checkup age. They are the right tool to decide whether to talk to a doctor. Our milestones by month page lists them all.
- The WHO Motor Development Study followed healthy babies in Ghana, India, Norway, Oman and the United States and measured the full window in which six big motor skills appear. It shows how wide "normal" is.
| Motor skill | WHO window (age in months) |
|---|---|
| Sitting without support | 3.8 to 9.2 |
| Standing with assistance | 4.8 to 11.4 |
| Hands-and-knees crawling | 5.2 to 13.5 |
| Walking with assistance | 6.0 to 13.7 |
| Standing alone | 6.9 to 16.9 |
| Walking alone | 8.2 to 17.6 |
Source: WHO Multicentre Growth Reference Study, windows of achievement table. In the same study, about 90% of children reached five of these skills in a common order, and 4.3% never crawled on hands and knees at all.
The sleep figures below come from the WHO 2019 guidelines: 14 to 17 hours per 24 hours from 0 to 3 months, and 12 to 16 hours from 4 to 11 months, naps included. More detail in baby sleep by age.
Months 0 to 1: getting to know the world
The first weeks are about feeding, sleeping and getting to know you: your voice, your smell, your face close to theirs. Long stretches of sleep, day and night, are normal at this age.
Play ideas (from the CDC 2-month tips): talk, read and sing to your baby; cuddle and hold them a lot; talk during feeds, changes and baths; start short sessions of supervised tummy time from the first days home.
Months 1 to 2: the first social smile
By 2 months, the CDC expects most babies to smile when you talk to them, look at your face, make sounds other than crying and hold their head up on their tummy.
Play ideas: copy your baby's sounds to start little "conversations"; shake a rattle on one side and see if they turn toward it; look at a baby-safe mirror or bright pictures together. Never shake your baby. If crying wears you down, put your baby somewhere safe, step away, and check on them every 5 to 10 minutes, as the CDC advises.
Months 3 to 4: hands, voices and laughter
Head control steadies. By 4 months, most babies coo, turn toward your voice, chuckle, bring hands to mouth, swing at toys and push up onto their forearms on their tummy.
Play ideas (CDC 4-month tips): lay your baby on their back and move a bright toy slowly side to side to see if they track it; play peek-a-boo; give easy-to-hold toys like rattles and cloth books; and avoid keeping your baby in swings, strollers or bouncers for long stretches. WHO guidelines say babies should not be restrained for more than 1 hour at a time.
Months 5 to 6: rolling and reaching
By 6 months, most babies roll from tummy to back, push up on straight arms, lean on their hands when sitting, laugh, squeal and blow raspberries. Everything goes in the mouth: that is how they explore.
Around 6 months is also when most families begin solid food. The CDC suggests talking with your baby's doctor about when to start. See starting solids.
Play ideas (CDC 6-month tips): put toys just out of reach to encourage rolling; hold your baby up while they sit so they can practise balance; point at things on a walk and name them; when they drop a toy, hand it back — it teaches cause and effect.
Months 7 to 9: sitting, babbling and strangers
Many babies sit alone and start moving across the floor: crawling, scooting or rolling. By 9 months, most babbles "mamamama" or "bababa", lift their arms to be picked up, look for a dropped spoon and may be shy or clingy with strangers. Separation feelings are a sign of a strong bond, not a problem.
Play ideas (CDC 9-month tips): place toys a little out of reach on a play mat; play "my turn, your turn" by passing a toy back and forth; hide a toy under a blanket and let your baby find it; say a quick, cheerful goodbye rather than sneaking away. Baby-proof now: move breakable things, lock away medicines and cleaning products, and save the Poison Help Line (800-222-1222 in the US) in your phone.
Months 10 to 12: standing and first words
By 12 months, most babies pull up to stand, walk holding on to furniture, pick up small bits of food between thumb and finger, wave bye-bye, call you "mama" or "dada" and understand "no".
Play ideas (CDC 1-year tips): name what your baby points at; give push toys, boxes or a small sturdy chair to walk behind; play with blocks; read books with textures or flaps. The CDC advises avoiding baby walkers.
Through the whole first year
- Screens: the WHO and the CDC do not recommend screen time before age 2, video calls with loved ones aside. Details in screen time by age.
- Floor time: WHO guidelines ask for active play several times a day, including at least 30 minutes on the tummy spread across the day.
- Your well-being matters: the CDC repeats it at every age. Parenting is easier to enjoy when you are looked after too.
If anything in this timeline worries you, or your baby loses a skill they had, talk to your pediatrician or health visitor. The milestones by month page explains when to act early.
Questions parents ask
When do babies sit up on their own?
In the WHO motor study, healthy babies sat without support anywhere between 3.8 and 9.2 months. The CDC lists sitting without support among the things most babies do by 9 months.
When do babies start walking?
The WHO window for walking alone runs from 8.2 to 17.6 months. By 12 months, the CDC expects most babies to pull up to stand and walk holding on to furniture, and by 18 months to walk without holding on.
Should I use a baby walker to help my baby walk?
No. The CDC advises avoiding baby walkers and letting your baby hold your hands or stable furniture to practise instead.
How much sleep does a baby need in the first year?
WHO guidelines give 14 to 17 hours a day, naps included, from 0 to 3 months, and 12 to 16 hours from 4 to 11 months.
Sources
- WHO — Windows of achievement for six gross motor milestones (Multicentre Growth Reference Study) checked October 13, 2026
- WHO Multicentre Growth Reference Study Group. WHO Motor Development Study, windows of achievement for six gross motor development milestones. Acta Paediatrica, 2006 checked October 13, 2026
- CDC — Milestones by age, with tips and activities for each age checked October 13, 2026
- WHO — To grow up healthy, children need to sit less and play more (2019 guidelines for children under 5) checked October 13, 2026
Mamavela explains; it does not replace your midwife, doctor or pediatrician, who know your situation. If something worries you, call them. In an emergency, call 911 (US), 999 (UK) or 112.