Your 5-Month-Old: Mouthing Everything, Sounds Copied Back
By the Growbaby team · Published Aug 4, 2026
Written against AAP, CDC and WHO guidance. How we write these guides
At a glance
- The mouth is now an investigating tool, not just a feeding one.
- Babies start copying the sounds you make, which is where conversation begins.
- Sitting with support arrives for many babies this month.
- Both hands start working together on the same object.
- Solids are still not recommended yet; around 6 months is the usual guidance.
Everything goes in the mouth this month, and it is worth reframing that before it becomes a battle. The mouth has more nerve endings than the hands do at this age, so mouthing is how your baby finds out what something is made of. The job is to make what is within reach safe, not to stop the behavior.
The other change is social. Make a sound and your baby may make it back. That exchange, sound out and sound returned, is the shape every conversation they will ever have is built on, so it is worth answering every time.
What is new this month
Mouthing is investigation, not a habit to break. At this age the mouth carries more sensory information than the hands do, so putting something in it is how your baby finds out whether it is hard, cold, rough or heavy. The job is making what is in reach safe rather than stopping the behavior.
Copying a sound back is the other change, and it is bigger than it looks. A sound offered and a sound returned is the exchange every conversation is built from, long before any of it is words. Answering every time is genuinely how it develops.
Week by week, in the app
One thing to notice and one thing to try, for every week of the first three years. Here is what this month covers. The app works out which week your child is in from their birth date and brings each one to you on the day.
- Week 18Your baby is Exploring with Their Mouth
- Week 19Your baby is Imitating Sounds
- Week 20Your baby is Sitting with Support
- Week 21Your baby is Getting Closer to Sitting Independently
- Week 22Your baby is Holding Objects with Both Hands
Read next
- Newborn Noises: Hiccups, Grunts, Sneezes and What Is NormalGrunts, squeaks, sighs, sneezes and hiccups are all listed by the AAP as ordinary newborn noise.
- When Do Babies Roll Over?Tummy to back usually comes first, at around five to six months.
- When Do Babies Start Crawling?Most babies start moving across the floor somewhere between 6 and 10 months.
This week, for your baby
Growbaby works out which week your baby is in from their birth date and brings that week's activity to you on the day, so you are not looking up where you are. Plus adaptive soothing for the nights and Growy for the questions in between.
Frequently asked questions
Because at five months the mouth is a better instrument than the hands, and it stays that way for a while. The practical consequence is a housekeeping one rather than a behavioural one: this is the month to get down to floor level and look at what is actually within arm's reach, because all of it is going in.
Around six months is the usual guidance, and five months is still too early for most babies. Milk stays the main event well past the first spoonful.
Supported sitting arrives for many babies around now. Unsupported sitting is further off than most articles suggest: the CDC lists leaning on the hands to stay upright at six months and sitting without support at nine, not at seven. Propping a baby who cannot yet hold the position does not speed any of it up.
This guide is for general informational purposes only. Growbaby is not a medical device and does not provide medical advice, diagnosis or treatment. Every baby develops at their own pace; for any question or concern about your baby's health or development, always consult your pediatrician or another qualified healthcare provider.