4 month old baby

What a 4 month old baby is doing

Four months is a visible jump. The HSE describes a baby who can hold their head steady in line with their body, so it no longer lags behind the shoulders when they are lifted, and who may roll from front to back. They will sit with their back supported on your lap, clutch at objects, and reach out and move their hands while lying on their back.

The sound changes too. Your baby will laugh out loud, move their body towards a voice, make sounds like "ah-goo", focus on people who are talking, and make a vocal sound when a person stops talking — the first outline of taking turns in a conversation. Socially, your baby will recognise their mother. They will reach for objects and look at them while holding them.

Rolling is the milestone parents watch hardest at four months. It is listed as something a baby "may" do, not "will", and rolling back to front generally comes later, around six months. A baby who is not rolling at four months but is reaching, batting and holding their head steady is on the described path, and the HSE is explicit that its milestone ages are averages.

The 16 week vaccinations

The UK schedule offers two vaccines at 16 weeks: the third dose of the 6-in-1 and the first dose of the pneumococcal vaccine. Note what is not there. There is no third rotavirus dose, because the course is two doses, and MenB does not appear again until one year. If a chart you have seen shows something different, check its date and the country it applies to, because schedules are revised and doses move between ages.

NHS inform lists what tends to follow. After the pneumococcal vaccine, a mild fever, diarrhoea, vomiting or a rash. After the 6-in-1, diarrhoea, vomiting or a mild fever. The general picture applies to any vaccination: swelling, pain, redness, bruising or a hard lump where the injection was given, sleepiness, irritability, being upset and less appetite than usual, usually passing within a couple of days. It is normal for a baby to be upset for up to 48 hours, and a cuddle, extra drinks and a walk in fresh air are the suggested comfort.

The four month sleep regression

More people search for four-month sleep problems than for four-month milestones, and the term "sleep regression" is worth putting in context first: it comes from parenting and sleep-consulting culture, not from clinical guidance. What the NHS describes is the ordinary instability of the first two years — as your baby grows their sleep pattern will change, and it can feel as though every time you have settled into a routine it changes again.

The published NHS range for three to six months is still wide: fewer night feeds mean your baby may be able to sleep longer, and some babies may sleep eight hours or longer at night, but not all will. A four-month-old waking more than they did at ten weeks is not outside that. Our sleep regressions guide covers what is thought to change at four, eight and twelve months and how long the disruption usually runs.

Two things are worth holding steady while it passes: a calm, consistent bedtime, and safe sleep exactly as it was. Our safe sleep guide has the full list. If your baby has started rolling, that is a reason to check the cot is clear, not a reason to relax any of it.

Feeding at 4 months, and the food chart problem

Four-month food charts and weaning recipes are all over search results, and the NHS position is that solids should start at around six months. Its reasons are specific: breast milk or first infant formula provides the energy and nutrients your baby needs until around six months, waiting gives your baby time to develop so they can cope fully with solid foods, and a baby who waits is more able to feed themselves and better at moving food around their mouth, chewing and swallowing.

The NHS also lists the behaviours that get mistaken for readiness at exactly this age: chewing fists, waking in the night more than usual, and wanting extra milk feeds. All are normal, and none of them mean a baby is ready, nor will starting solids make a baby sleep through the night. If your baby was born prematurely, the NHS asks you to check with your health visitor or GP about when to start rather than counting from the birth date.

Milk amounts are still not published per age. Feed responsively, do not force a feed to be finished, and use wet nappies and weight gain as your check.

Babies born early

Development at four months is judged on corrected age, worked out from your original due date rather than the birth date. Our adjusted age calculator will do the arithmetic before you compare your baby to anything here, and it is worth mentioning the corrected age at every appointment.

What is worth raising

The HSE's four-month list is the longest of the early months. Contact a GP or public health nurse if your baby does not make eye contact when you speak to them, does not fix on something and follow it with their eyes, does not grasp objects placed in their hands, cannot lift their head for short periods on their tummy, cannot hold their head steady, does not coo or make sounds, does not bring things to their mouth, or loses skills they had before.

When to get urgent help

For a baby aged three to six months, the NHS threshold for calling 111 is a temperature of 39C or higher, or if you think they have a high temperature. Call regardless of the reading if there are other signs of illness, if feeding drops sharply, if wet nappies become far fewer, if your baby is hard to wake, or if breathing looks like hard work.