4 months old

Development

Around four months, reaching stops being accidental and becomes purposeful. Your baby starts to see a toy, decide they want it, and send a hand out to get it — often landing on it, sometimes missing, and either way learning fast from the attempt. Once an object is in hand it heads straight for the mouth. That mouthing is your baby's most sophisticated way of investigating the world right now; it is normal exploration and does not by itself mean teething. You will also see them bring both hands to the middle to hold and turn a toy, studying it with real concentration.

This is also when many babies begin to roll, most often front-to-back first because it takes less coordination. Rolling rarely arrives on a schedule — it can appear suddenly one afternoon, or build up over a couple of weeks of near-misses — and the range of normal is wide. Alongside the physical changes, your baby is becoming far more social: longer stretches of eye contact, open-mouthed smiles, and delighted reactions when you talk or play back. If a particular skill hasn't appeared yet, that alone is usually not a concern; if you ever feel unsure about your baby's movement or responsiveness, your healthcare professional is the right person to ask.

Sleep

Four months is famous — sometimes dreaded — for sleep that suddenly falls apart. Nights that were settling can break up again, naps can shorten, and a baby who dropped off easily may start needing more help. It is worth understanding what's actually happening: this is not a step backwards, but a permanent maturing of how your baby sleeps. Their sleep is reorganising into more adult-like cycles with lighter phases between the deep ones, and at the surface of each cycle they briefly rouse. Learning to drift back down through those wake-ups is a genuinely new skill, and it takes practice.

Because the change is developmental rather than a problem to fix, the most helpful response is usually steadiness rather than a big new plan. Hold gently to the routines and comfort your baby already knows — the familiar wind-down, the calm room, the predictable order of things — so the path to sleep stays recognisable even while the underlying wiring shifts. Keeping an eye on awake times matters more than usual now, since an overtired baby settles even less easily during this stretch. For most families it eases within a few weeks. If broken sleep is wearing you down, that is worth naming out loud and, if it helps, raising with your healthcare professional. Our guide on sleep regressions goes into what to expect and how to ride it out.

Play

Play at four months is quietly building the strength for everything coming next. Continuing daily supervised tummy time — in short, frequent sessions rather than one long stretch — develops the neck, shoulder, and back muscles your baby will draw on to roll, sit, and eventually crawl. If your baby dislikes being on their tummy, keep the sessions brief and get down at their level, face to face, or prop a small mirror in front of them; your presence usually turns protest into curiosity.

Beyond tummy time, floor play with a few interesting objects placed just within reach — and one or two placed just beyond it — invites all that new purposeful reaching. High-contrast patterns, gentle rattles, and toys that respond when grabbed are especially engaging now. You don't need much, and you don't need to entertain constantly: short bursts of shared attention, plenty of talking about what you're both looking at, and room to practise the same movement over and over are exactly what this age thrives on.