1 Month Old: Your Baby's Development From Week 4 to Week 6

The first month of a baby's life is often experienced by parents in a fog of exhaustion and wonder in roughly equal measure. By the time your baby reaches 4 weeks, the initial shock of newborn life has given way to something approaching a routine, and the baby you see now is noticeably different from the one who arrived. The period from 4 to 6 weeks is particularly significant, both developmentally and medically.

How Much Has Already Changed

At birth, your baby's vision was limited to approximately 20 to 30 centimetres — roughly the distance from the crook of your arm to your face during feeding. Their hearing was functional but undifferentiated. Their waking time was brief and mostly associated with feeding.

By 4 weeks, significant development has occurred. Your baby is becoming more aware of faces, can track a slowly moving object with their eyes, is beginning to distinguish your voice from other voices, and may already be showing the very earliest signs of social responsiveness.

Social Smiling: The Milestone That Changes Everything

The social smile — a real, responsive smile in reaction to a human face or voice — typically emerges between 4 and 8 weeks, with many babies producing their first clear social smiles around the 5 to 6 week mark.

Before this, babies may produce reflex smiles, particularly during sleep, which are not responses to social interaction. Social smiling is different: it is a direct, intentional response to a face or voice, often accompanied by widened eyes, increased alertness, and sometimes excited limb movements.

The significance of the social smile is hard to overstate for parents. After weeks of round-the-clock feeding and settling, the first genuine smile in response to your face is a profound shift in the relationship. It confirms that your baby knows you, sees you, and is beginning to engage with the world beyond their basic needs.

If your baby has not produced any social smiles by 8 weeks, mention it at your next health visitor check. Lack of social smiling by 3 months is a developmental red flag that warrants further assessment.

Longer Alert Periods

In the first weeks, most babies are awake primarily to feed and return to sleep relatively quickly. Between 4 and 6 weeks, many babies begin to have longer stretches of genuine alertness — periods where they are awake, calm, and interested in the environment, without immediately needing to feed or being on the verge of sleep.

These alert periods are precious developmental time. Your baby is taking in information about faces, voices, colours, and movement. Talking to them, singing, holding them in a position where they can see your face, and offering simple visual stimulation (high-contrast black and white patterns are particularly effective for young eyes) all support development during these windows.

Alert periods at this age are typically short — 10 to 45 minutes — before the baby begins to show tired signs. Watch for tired cues (eyes glazing, looking away, yawning, fussiness) and begin settling before they become overtired. Overtired babies at this age are significantly harder to settle than those who go down slightly tired.

Tummy Time at 4 to 6 Weeks

Tummy time is the practice of placing a baby on their tummy while awake and supervised. It is important for several reasons: it builds neck, shoulder, and upper body strength that later supports sitting, crawling, and standing; it prevents flat spots developing on the back of the head (positional plagiocephaly); and it provides a different sensory perspective on the world.

At 4 to 6 weeks, tummy time is brief — one to three minutes at a time — and may be strongly resisted by the baby. This resistance is normal. Very few 4-week-olds enjoy tummy time. The goal is not enjoyment but exposure and gradual building of strength.

Making tummy time more manageable:

• Place the baby on your chest in a semi-reclined position — this is tummy time and most babies tolerate it better than floor-based tummy time
• Use a rolled muslin or small tummy time pillow under the baby's chest to help them see further ahead
• Get down to their level on the floor and interact with them — your face is their strongest incentive to lift their head
• Keep sessions very short and frequent (three to five times per day) rather than one long session

By 6 weeks, many babies can briefly lift their head off the surface during tummy time, holding it for a few seconds before it drops back down. This is a genuine achievement.

Feeding at 4 to 6 Weeks

Feeding patterns at 4 to 6 weeks are still very frequent, particularly for breastfed babies. Many breastfed babies this age are still feeding every 2 to 3 hours, and cluster feeding in the evenings — a pattern of very frequent, close-together feeds for several hours — is common and does not indicate low supply.

The 6-week growth spurt (described elsewhere) often falls within this window and is one of the most significant feeding disruptions of the first three months.

For formula-fed babies, volumes at this age are typically in the range of 120 to 180ml every 3 to 4 hours, but individual variation is wide. Follow your baby's hunger cues rather than a rigid schedule.

The 6-Week Check

At 6 weeks (sometimes at 8 weeks in some NHS areas), your baby will have a review with a GP. This check covers:

• Physical examination: heart, hips, eyes, testicular descent in boys, spine, and general tone
• Head circumference, weight, and length measurement plotted on growth charts
• Reflexes and responsiveness
• Questions about feeding, sleep, and your own wellbeing

This is also the point at which you, the parent, will have a postnatal check. This matters. The 6-week maternal check often addresses emotional wellbeing, pelvic floor function, and contraception — but it is brief, and you may need to raise your own concerns proactively rather than waiting to be asked.

Prepare a list of any concerns before the appointment. The check is short, and it is easy to forget things in the moment, particularly if your baby is unsettled or has just been fed.

What to Watch For

Between 4 and 8 weeks, the following warrant a prompt conversation with your health visitor or GP:

• No social smiling by 8 weeks
• Persistent difficulty feeding or failing to regain and exceed birth weight
• Any concerns about your own mental health — postnatal depression and anxiety commonly present in the first 6 weeks
• Any signs of illness: a fever of 38 degrees or above in a baby this young requires same-day medical attention

The weeks from 4 to 6 are hard. But they also mark the beginning of the baby beginning to come towards you — the first glimmers of the relationship that will define the next several years.