3 week old baby development

by Georgia Aspinall |

Wow, how quickly is time going? Your baby is three weeks old! From baby sleep to first smiles, colic and sleep associations, here’s what to expect as your baby reaches this milestone.

In this article:

  • What can you expect when your baby is three weeks old?

  • How should a 3-week-old baby be physically developing?

  • How should a 3-week-old baby be cognitively developing?

  • What jabs should a 3-week-old baby have?

  • How much should a 3-week-old baby be sleeping?

  • How much should a 3-week-old baby be eating?

  • Colic in your 3-week-old baby

  • How much should a 3-week-old baby be pooing?

  • Milestones of your 3-week-old baby

  • What problems should parents of aware of at three weeks?

What can you expect when your baby is three weeks old?

You may be getting more used to your new life with your newborn, but there’s still plenty of questions to be answered as they grow more and more each day.

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1) They love to watch you

Whatever you're doing, they are obsessed with your every move! They will love to watch you and may look like they are carefully studying your facial expressions or when you're chatting to some other adults, listening to what you're saying.

How should a 3-week-old baby be physically developing?

Remember those ‘newborn babies’ on TV that you assumed looked just like the real thing? By the third week, your baby is likely to look more like that. Baby's skin should be peeling less and looking more plump, pink and clear.

While your baby's nervous system and muscle control are yet to mature, you’ll find their movements to be jerky. Don’t worry, these will become more fluid as their muscles get stronger.

To speed up the process of lifting their own head, your baby needs to spend more time on their stomach while they are awake - babies should always sleep on their back. This helps strengthen the neck muscles so they can push up to sit, roll over and crawl. It will also reduce the likelihood of your baby developing a flat spot on the back of their head from always being on their back.

Put your face in front of your baby's while they’re on their stomach, as this will encourage them to look up at you and start to lift their head and move it from side to side more.

How should a 3-week-old baby be cognitively developing?

Your baby may now be recognising songs or sounds they heard when they were in the womb, proving baby's start learning before they enter the world. They will also start realising they can make specific things happen, but they will find it difficult to remember what they've learned. Don’t worry, their memory will improve as the weeks go on.

Your baby can still only see what's 8-12 inches in front of them but they might start to recognise your face. They will still only see things in black and white, with shades of gray and will slowly start to develop their colour vision at around 4 months. The best thing you can do to improve your baby’s development at this stage is to allow them to study your face and copy your lip movements. They will start to develop subtle cues you may notice if you watch carefully.

Find toys perfect for your baby's age to speed this process up, but not too many at one time as your baby needs to learn to concentrate on one thing.

What jabs should a 3-week-old baby have?

You have another five weeks before your baby needs any jabs, but if you want to prepare for your baby's first vaccinations, check out our handy tips.

How much should a 3-week-old baby be sleeping?

sleeping newborn

In two words – a lot! During the first few weeks of a baby’s life, they need 18 hours a day of sleep, with frequent feeds in between. It sounds peaceful, but by now you know it’s anything but that. It’s not too early to start teaching them a sleeping schedule though. Establish the difference between night and day by not altering your own activities during daylight hours. When it’s daytime, keep the house bright and noise levels normal, then at night time make sure not to play or fuss too much when they wake upkeep the house dark and peaceful. That way your baby will begin to recognise that night time is for sleeping.

If you’re finding the erratic sleeping schedule difficult, check out how to fix these sleep mistakes new parents always make in the first few weeks. Finally, don’t worry if everyone in your mummy group seems to be getting more sleep than you are, you are doing a great job - some babies are just better sleepers.

How much should a 3-week-old baby be eating?

Whether you're nursing or giving your baby formula, it’s difficult for a baby to overeat at this stage, so don’t worry if your baby seems to be consuming more than you thought. For a basic guideline, measure your baby's weight and then feed them 150ml-200ml per kilo. The best thing you can do is feed whenever they need it, as babies typically know exactly how much food they need at this stage.

If you’re breastfeeding, it may be more difficult to know how much breast milk your baby is having, but as long as they are latching on and is feeding until they want to stop, all is ok. Check out these tips on the best positions to try when breastfeeding.

Colic in your 3-week-old baby

Affecting up to 40 per cent of babies, colic is a normal fear for many parents. It’s uncontrollable and meaningless crying that can be exhausting for you. However, it is thought to dissipate by three months – which probably still feels like a long way off right now. The best thing you can do is figure out whether your baby is experiencing colic, or if there is another reason, such as a urinary infection. Take your baby to the doctors if you notice the signs of colic which are:

  • Crying for more than three hours at a time, three times a week for at least three weeks.

  • Intense crying with tight fists and legs, which you are unable to soothe

  • These usually occur suddenly in the evening

There is no definite cause of colic but it often occurs during the 3 to 6-week mark in your baby’s life. Taking your baby to the doctors will help establish the best course of action to reduce it. In the meantime, check out our ten top tips on dealing with colic.

How much should a 3-week-old baby be pooing?

Every baby is different; some may poo straight after a meal or others may be less regular. As long as your baby is pooing between one and ten times a day, they’re within the norm. If you’re worried about the poo itself, check out our poo colour chart.

Milestones of your 3-week-old baby

  • The first smile: By three weeks, your baby may be trying out their first smile, copying your face movements and poking their tongue out. They may even start making sounds other than crying, who’d of thought it?

  • Tummy time: As we mentioned earlier, now is the time your baby should be on their stomach and strengthening those neck muscles. Sooner or later they’ll be running around all over the place, so take solace in these precious moments you can keep them somewhat still!

  • Are you going it alone? If your partner has returned to work, you may be starting to feel lonely in your everyday activities. It’s a good time to join some parenting groups and meet up with some other new parents. Don’t forget, you can always try shared parental leave so you’re both home for the same amount of time.

What problems should parents of aware of at three weeks?

  • Sleep deprivation: After three weeks of interrupted sleep, you’re bound to feel the effects of sleep deprivation right now. Check out these foods that help beat exhaustion. We also know a bunch of new mummy makeup products you can use to look more awake, even if you don’t feel it!

  • Postnatal Depression: Your hormones should be settling now, and that means bye-bye baby blues. If you’re still struggling with feelings of failure or as though everything could go wrong as it’s your fault you may be experiencing postnatal depression. Take a trip down to your doctor for advice on how to handle it, it’s the best thing you can do to stay healthy for your baby. Here are some of the key differences between baby blues and postnatal depression. If you do find yourself struggling with postnatal depression, remember this doesn't make you a bad mother and is a condition that affects one in ten women.

  • Pelvic floor: Your pelvic floor is the sling of muscle that keeps you in shape downstairs. Nine months of supporting a baby has stretched it. Exercises will help it back into shape, and aid bladder control. ‘Imagine you need to hold in a wee and a poo - and squeeze!’ says Dr Ellie Cannon. ‘Repeat this for five minutes every time you feed your baby. As you become stronger, try holding in your tummy muscles at the same time.’

  • Sore breasts: Breasts that are working hard to feed a baby can get painful. Keep a couple of clean nappies in the freezer. After a feed, place them in your bra to cool and soothe.

  • Baby sick: As you cuddle your baby against your shoulder, they’ll bring up regurgitated dribbles. ‘A newborn has a very small stomach that can’t handle much milk,’ says Ellie. ‘And the muscle that keeps the milk in his stomach isn’t very strong.’ A muslin saves the day.

  • Be aware of sleep associations: A newborn baby usually only wakes up when they are hungry. But as the weeks go on, that starts to change, and they build sleep associations. ‘Whatever you do now to help them get to sleep, such as rocking or feeding, they’ll want you to keep doing,’ says Ellie. ‘Put your baby down to sleep when they're awake. Let them nod off on their own or with a lullaby.’

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