Smiles, chuckles and discovering those hands
Your baby is becoming wonderfully sociable — smiling at you on purpose, cooing back when you chat, and staring at their own hands like they've just found treasure. Towards the end of this stage, UK babies have their 16-week vaccinations.
Development
Expect proper social smiles now, and maybe the first chuckles when you play. Many babies this age coo back and forth with you — it's your first real conversation, so do reply.
Head control is getting steadier when you hold them upright, and in tummy time many babies push up onto their forearms. Hands are the discovery of the month: watched intently, brought to the mouth, and swung hopefully at toys.
Every baby does these things on their own timetable. The ages here are when most babies have got there, not a test to pass.
Sleep
Some babies start doing a longer stretch at night around now; plenty don't yet. Naps are usually still short and scattered — a predictable nap rhythm tends to come later.
Keep the safer sleep basics going: on their back for every sleep, in a clear flat cot or Moses basket, in your room for at least the first 6 months.
Watch for early signs of rolling — wriggling onto the side, swinging legs over. The Lullaby Trust advises stopping arms-in swaddling as soon as any signs of rolling appear.
And you
In the UK, the 16-week vaccinations land at the end of this stage — currently the third 6-in-1 dose and the first pneumococcal dose. The schedule was updated in 2025, so the NHS vaccinations page always has the current list. In the US, this roughly lines up with the 4-month well-child visit.
Days may be finding a loose rhythm, and the intense crying of the early weeks has usually eased. If it doesn't feel easier — or you feel low, flat or anxious — please say so to your health visitor or GP. Postnatal depression can start at any point in the first year, and help works.
Feeding at this stage
Pick how you're feeding — we'll remember for next time. Every one of these is a good way to feed a baby.
Breastfeeding
- Feeds often get much quicker around now — an efficient baby can empty a breast in a few minutes, so short feeds usually mean skill, not a problem.
- Softer breasts don't mean your supply has dropped; it has simply settled to match what your baby takes.
- A day or two of near-constant feeding is often a growth spurt — feed through it and things settle again.
Breast + expressed
- Pumping output per session often steadies around now — a settled amount is normal, not a decline.
- Date your frozen milk and use the oldest first, so the stash keeps rotating.
- Paced bottle feeding — baby fairly upright, slow-flow teat, little breaks — keeps bottle feeds calm and lets your baby set the pace.
Breast + formula
- Keeping your breastfeeds at roughly consistent times of day helps your supply stay steady around the formula feeds.
- There's no required order or ratio — follow your baby's cues rather than the clock, and adjust as you go.
- Whatever mix you've settled on, it's feeding your baby and it counts — combination feeding is a completely valid way to do this.
Formula
- As a rough NHS guide, babies need about 150–200ml of formula per kilogram of body weight a day until around 6 months — but appetites genuinely vary, so let your baby lead.
- Plenty of wet nappies and steady weight gain are much more helpful signs than exact millilitres.
- Watch for pauses and turning away during feeds — stopping when your baby says so helps them keep a healthy sense of their own appetite.
Totally normal (even when it doesn't feel it)
- Feeds that suddenly take five minutes instead of forty — that's efficiency, not a supply problem.
- Breastfed babies can start pooing much less often around now; even several days between soft poos can be normal.
- Dribbling and fist-chewing at this age are usually just exploration, not necessarily teething.
- Short, chaotic naps with no pattern — nap rhythm usually arrives in the months ahead.
- A clingy, fussy day or two out of nowhere — growth spurts and busy brains pass.
- Mild fussiness or a slightly raised temperature after the 16-week jabs is common and short-lived.
Worth checking
You know your baby best — if any of these ring true, or something just feels off, it's always OK to ask.
- Your baby isn't smiling back at you yet.
- They don't startle at, settle to, or turn towards voices and sounds.
- They don't follow your face or a toy with their eyes.
- Their head still feels very wobbly when you hold them upright at around 4 months.
- They feel unusually stiff, or unusually floppy, when you pick them up.
- They strongly favour one side — head always turned the same way, or one arm doing all the work.
- You know your baby best — if anything here rings true, or something else is niggling, a chat with your health visitor or GP (or your baby's doctor elsewhere) is never wasted.