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Baby 4 weeks old

Medically reviewed by

Sarah Connor, MD Jul 5, 2026

Quick Facts

Age	4 weeks (approximately 1 month)
Average Length	50–54 cm
Average Weight	3.5–4.5 kg
Daily Sleep	4–17 hours (in short cycles)
Feedings per Day	6–8 times
Feeding Amount	~60–120 ml (2–4 oz) per feeding

Key Takeaways

Your baby is becoming more alert and may begin to briefly focus on your face and track movement.

Most 4 week old babies feed 6–8 times per day, taking approximately 60–120 ml (2–4 oz) per feeding

Short tummy time sessions — 1–2 minutes, 3–4 times per day — help build neck and shoulder strength.

Your Baby at 4 Weeks Old

Your 4 week old baby is beginning to emerge from the sleepy haze of the newborn stage — and so are you. This week, you may notice slightly longer stretches of alertness, more eye contact, and early signs of recognition when they hear your voice. It's a small but meaningful shift.

Week 4 is also a time when many parents start to settle into some kind of rhythm, even if feeding and sleep are still unpredictable. This guide covers what to expect developmentally, how to support healthy feeding and sleep, and what's normal to experience at this stage — for your baby and for you.

4 Weeks Old Baby Development: Milestones & Growth

Physical Development

At 4 weeks, your baby is gaining around 150–200 grams per week and growing approximately 2.5 cm per month. Their movements are still reflexive and often jerky, but muscle coordination is improving. During tummy time, many babies can briefly lift their head and turn it from side to side — an early sign of neck strength building.

Vision

Your baby's vision is still developing and is clearest at a distance of about 20–30 cm — roughly the distance to your face during feeding. They are particularly drawn to high-contrast patterns, faces, and objects that move slowly. You may catch them staring intently at your face or a nearby window.

Hearing & Recognition

Your baby's hearing is well-developed from birth, and by 4 weeks they are beginning to recognise familiar voices — especially yours. Familiar sounds can be soothing, which is why your baby may calm down when you speak, sing, or hum to them. Loud or unexpected noises may cause a startle reflex (the Moro reflex), which is entirely normal at this age.

Your Life This Week: The Parent Experience

By week 4, you may feel slightly more confident in reading your baby's cues — though that doesn't mean it gets easy overnight. Sleep deprivation is still significant for most parents, and emotional highs and lows are completely normal.

If you haven't already, introducing a loose daily rhythm (rather than a strict schedule) can help bring some predictability to your day: feeding, a period of awake time, sleep, repeat. Your baby's circadian rhythm is not yet established, so this is about gentle structure, not rigid timing.

If you are experiencing persistent sadness, anxiety, or feeling disconnected from your baby, please speak to your health visitor or GP. Postnatal depression and anxiety affect up to 1 in 5 new mothers and up to 1 in 10 fathers — it is common, treatable, and nothing to be ashamed of.

What to Do This Week: Practical Checklist

DEVELOPMENT & PLAY

Aim for 1–2 minutes, 3–4 times per day. Place your baby on a firm, flat surface while you are present. It builds neck, shoulder, and core strength. Tummy time
Describe what you're doing as you go about your day. Early exposure to language shapes cognitive development. Talk and narrate
Continue to offer skin-to-skin time — it regulates your baby's temperature, heart rate, and stress response, and deepens bonding. Skin-to-skin contact

ROUTINES & SLEEP

Yawning, looking away, or rubbing their face signals tiredness. Put your baby down drowsy but awake if possible. Watch for sleep cues
Expose your baby to natural light and gentle stimulation during the day; keep night feeds calm and quiet. Day vs night
Always place your baby on their back, in their own sleep space, with no loose bedding or toys. Safe sleep

HEALTH

Your baby's 6-week developmental review and your own postnatal check are coming up — confirm your appointment with your GP or health visitor. 6-week check
Current UK guidelines recommend daily vitamin D drops for all breastfed babies from birth, and for formula-fed babies consuming less than 500 ml of formula per day. Vitamin D

Feeding Your 4 Weeks Old Baby

At 4 weeks, your baby will typically feed 6–8 times per day, with around 60–120 ml (2–4 oz) per feeding. Total daily intake for formula-fed babies is generally around 150–200 ml per kg of body weight per day — so a baby weighing 4 kg would take approximately 600–800 ml across 24 hours.

Feeding patterns may vary significantly from day to day, particularly around growth spurts — which commonly occur at around 3 weeks and 6 weeks. During a growth spurt, your baby may feed more frequently and seem harder to satisfy. This usually settles within a few days.

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Sleep at 4 Weeks : What's Normal & How to Help

Your 4 week old baby will sleep approximately 14–17 hours per day — but this is spread across many short cycles of 45 minutes to 3 hours, with no predictable night consolidation yet. A newborn's circadian rhythm does not begin to mature until around 6–8 weeks, so it is too early to expect longer overnight stretches.

To gently begin establishing a day-night difference, expose your baby to natural light and normal household noise during the day, and keep nighttime feeds calm, dimly lit, and quiet. This helps their developing circadian rhythm begin to differentiate between day and night.

Always follow safe sleep guidelines: firm, flat surface, on their back, in a clear sleep space. Room-sharing (but not bed-sharing) is recommended for the first 6 months as it reduces the risk of SIDS.

When to Contact Your Doctor or Midwife

Your baby has not regained their birth weight by 2–3 weeks or is losing weight after this point.
Your baby is feeding fewer than 6 times in 24 hours, or producing fewer than 6 wet nappies per day.
Your baby has a fever above 38°C — this always warrants immediate medical attention in babies under 3 months.
You notice persistent yellowing of the skin or whites of the eyes (jaundice) after the first 2 weeks.
Your baby is unusually limp, difficult to rouse, or not responding to sound or touch.
You have concerns about your own mental health — speak to your GP or health visitor.

Frequently Asked Questions

How much should a 4 week old baby eat?

Most 4 week old babies eat every 2–4 hours. Breastfed babies usually feed 8–12 times a day, while formula-fed babies often drink around 90–120 ml (3–4 oz) per feeding.

Why is my 4 week old baby so fussy?

Fussiness at 4 weeks is very common and can be caused by hunger, gas, tiredness, overstimulation, or a growth spurt. Babies are still adjusting to the world and often need extra comfort and cuddles.

When do 4 week old babies start smiling?

Some babies may show early smiles around 4 weeks, but true social smiles usually appear between 6–8 weeks. At this age, smiles are often brief and happen during calm or sleepy moments.