Month four is when personality bursts through. Belly laughs, deliberate grabbing, and the famous four-month sleep regression all show up together. Your baby is a much more active participant now.
4 months old developmental milestones
- Rolls from tummy to back
- Reaches for and grasps toys with both hands
- Belly laughs and squeals with delight
- Recognises familiar faces from across the room
- Sleep cycles reorganise (the 4-month "regression")
Care tips for 4 months old
- Move anything you’d rather baby didn’t grab out of reach — that once-safe coffee cup is now fair game.
- Never leave a roll-capable baby unattended on a bed, sofa, or changing table.
- Stick to the bedtime routine even during the regression — consistency is what carries you through.
- Extend tummy time to 15-30 minutes total across the day.
This month's checklist
- Baby-proof the floor
- Book the 4-month vaccinations
- Extend tummy time gradually
Frequently asked questions
Why is my 4-month-old suddenly not sleeping?
The 4-month sleep regression is a permanent shift in how baby sleeps — cycles become adult-like with more light-sleep transitions. Consistent wind-down and a dark room help.
Is my baby ready for solids?
Most guidelines recommend waiting until 6 months. Signs of readiness — sitting with support, losing the tongue-thrust reflex, showing interest in food — usually all arrive together closer to 6 months.
How much should a 4-month-old weigh?
Around 6.4-7.0 kg on average, but the growth curve matters more than a single number. Your paediatrician tracks this at every visit.
When to call your paediatrician
Most months of babyhood pass without alarm, but a small set of symptoms always deserves urgent review. Contact your paediatrician or the nearest paediatric emergency room straight away for any of the following:
- Fever above 39 °C, or any fever lasting more than 72 hours
- Refusing more than two feeds in a row, or fewer wet nappies than usual
- Breathing that is fast, noisy, or with visible chest tugging
- Persistent vomiting, blood in stool, or a swollen belly
- Any sudden loss of a skill baby had already learned
Where the 4 months old stage fits in
The first six months are all about building trust, feeding rhythms, and the neurological wiring that underpins every future skill. Growth is at its fastest — most babies gain 150-200 g per week early on and double their birth weight by six months. Your voice, your smell, and skin-to-skin contact are the most powerful tools you have.
Educational content — not a substitute for medical care. Contact your paediatrician urgently for high fever in a young infant, refusing feeds, laboured breathing, persistent vomiting, or any concern that feels wrong to you.