Baby development: stages, milestones and growth


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Watching your baby grow inside you during the different stages of pregnancy was NOTHING compared to what you get to witness during their first year of life. Seriously.

We talk a lot about how hard motherhood is, because, um, it’s really hard. But this stuff is what makes it oh so worth it. You’re gonna want plenty of space on your iPhone to capture photos and videos of the magic.

In this guide to your baby’s growth and development, we’ll touch on what to expect during the first weeks and months of their life. But first, a brief disclaimer: 

All babies grow and develop at different rates. They’re humans, not robots. They do their own thang. So don’t freak out if your child isn’t hitting every baby development milestone on the list in the right week or month. But if you ever ARE concerned about your baby’s development, it can’t hurt to mention it to your paediatrician.

That said, let’s look at baby development stages and growth expectations in their first year.


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Your newborn: typical growth and baby development by week

Week 1

Baby growth in Week 1

No matter what pregnancy complications you encountered, and what happened during labour to f*ck up your birth plan (it happens!), your baby has arrived. Whether they’re bigger or smaller than average isn’t a huge deal – what matters is that they grow consistently over time. So don’t compare your baby to others. But DO know that it’s completely normal for babies to lose between five and 10 percent of their birth weight in Week 1.


Baby development in Week 1

This first week is all about learning to live outside the womb. Pretty freaky stuff. Your newborn’s key priorities are breathing, feeding, sleeping, and pooping (lots of pooping).


Things to consider:


Week 2

Baby growth in Week 2

10–14 days after delivery, your baby will typically be back to their birth weight.

Baby development in Week 2

Your two-week-old will be sleeping up to 18 hours a day. It’s hard to manage impressive baby development milestones around that sleeping schedule, but if they’re crying, feeding and pooping lots, it’s a good sign.

Things to consider:
  • Your baby’s umbilical cord should have fallen off by now. Chat to your doctor if it hasn’t.

  • Skin-to-skin contact is great for your baby’s development (and okay, it’s great for basking in that sweet newborn scent too). It can also promote your breast milk supply. Win!

  • As your baby’s skin adjusts to life outside the womb, it might be susceptible to a variety of skin irritations (aka ‘rashes of doom’).

Week 3

Baby growth in Week 3

In the first few weeks, newborns typically gain around ⅔ of an ounce (20–30g) PER DAY, and grow 1.5–2 inches (4.5–5cm). So no, you’re not just imagining that your baby looks bigger every day. They actually are.

Baby development in Week 3

As your little one’s muscle strength grows, they may start to be able to lift their head for a few seconds or even turn their head side to side.

Things to consider:
  • It’s never too early to talk to your baby. They’re probably not great for conversation yet, but interacting with you, even this early on, is how they learn to think, move, express themselves and communicate.

  • Tummy time can help build muscle strength. Put your baby on their stomach on the floor for a few minutes each day. Always supervise.

  • Newborn sleep is f*cked. They might sleep 16–18 hrs a day, but they wake to feed unreasonably often and haven’t yet worked out that night is night.

  • Nothing is too silly to ask your paediatrician about. Ask away!

Week 4

Baby growth in Week 4

By now, you may have paid a few visits to your doctor or maternal child health nurse for growth checks, so you’ll have an idea of where your bub is tracking against the standardised baby growth chart. While wellbeing checks may vary state-to-state, you’ll generally have a few in your first few weeks. Remember – some babies are bigger, some are smaller, the main thing your doctor will check for is that they’re growing consistently.

Baby development in Week 4

By the end of their first month, your baby’s hearing should be fully developed. They may turn towards familiar sounds (your incredible operatic rendition of “Twinkle Twinkle Little Star”), and even make sweet, little cooing sounds themselves. 

Other four-week-old baby development milestones include natural reflexes like clutching, holding their head up, making fists, and thrashing their little limbs around like tiny psychotic orchestra conductors.

Things to consider:
  • Going for walks is great for your postpartum recovery, and for your baby’s development. They have so much to take in – Trees! Birds! Your local coffee shop! Choose a great pram, or invest in some sweet babywearing gear.

Week 5

Baby growth in Week 5

The median length of a five-week-old according to the official World Health Organization baby girl growth chart is 54.2cm (21.3 inches), while the baby boy growth chart lists 55.3cm (21.7 inches). So your baby is likely to have grown 5cm in the past five weeks! They may have even gone up a size or two already.

Baby development in Week 5

By Week 5, they’re likely to be able to hold small objects when placed in their hand, and may start holding their head up for a bit longer. They might even start using actions to communicate, like making noises to get your attention or wiggling when you come near (translation: “pick me UP, my milkmaid!”).

Things to consider:
  • It’s time for toys. Small sensory objects like rattles are a great option for babies at this age.

  • It’s never too early to start a bedtime routine. You might begin turning lights down in the evening, giving your baby a bath or massage, and generally getting them in a snoozey mood. But you might try all this and they still scream the house down. It’s known as ‘witching hour’ for a reason.

  • Don’t be alarmed if your baby drops a feed or two around Week 5. They may start sleeping for longer periods (yes please) and having longer, more consistent feeds.

Week 6

Baby growth in Week 6

A lot of babies experience a little growth spurt at around the six-week mark. It’s normal for your baby to have faster and slower periods of growth, so don’t worry if they don’t grow a whole lot one week – they’ll probably make up for it the next!

Baby development in Week 6

By now, your baby will start to get bored and need stimulation to stay content. They’ll also develop their own little ways of soothing themselves when they’re upset. Your bub might suck on their fist, for example. They might even learn to SMILE at you this week! Mama, get your camera on standby.

Things to note:
  • Check in with your paediatrician if your little one isn’t responding to loud noises, tracking movements with their eyes (i.e. when you walk across the room), smiling, putting their hands up to their mouth, or lifting their head during tummy time.

  • You’ll probably have a six-week postpartum checkup yourself this week. If you’re given the all-clear to resume sexual activites, USE PROTECTION (unless you’re ready for Baby #2).

Week 7

Baby growth in Week 7

The baby boy growth chart lists seven-week-olds at 57.1cm (22.5 inches) on average, while the baby girl growth chart lists them as 55.8cm (almost 22 inches). 

Just remember, your little one will be cruising along in their own baby growth percentile. So if they’re in the 15th percentile they’ll be smaller than the average, and if they’re in the 85th percentile they’ll be bigger. All’s swell as long as they’re healthy and following an upward trend in growth.

Baby development in Week 7

Your seven-week-old will start to develop an obsession with batting at hanging objects (beware dangly earrings). This is an important addition for tummy time as well, as your baby needs to build strength in their neck and arms.

Things to note:
  • Notice a flat spot on your baby’s head? Mention it to your paediatrician. It could be a sign they’re not turning their head enough.

  • You’ll probably have a two-month wellbeing checkup somewhere around weeks 7 or 8. Use it to ask any questions or raise concerns you have about your baby’s development or growth.

Holy sh*t they’re getting big: infant growth and baby development by month

2-3 months old

Baby growth at 2–3 months

Up until six months of age, most babies grow about 1.5–2.5cm (1/2 to 1 inches) a month, and gain about 140–200 grams (5 to 7 ounces) a week. While your arms might not appreciate the extra weight, at around 2–3 months your baby will start to develop that classic, adorable infant chubbiness.

Squeeze those chubba cheeks – it’s your motherly rite of passage.


Baby development at 2–3 months

By two-months old your baby will be able to recognise familiar faces, make gurgling noises (the foundations of learning to speak), and move their body with more purposeful movements. By three months, they’ll be able to sit up on your lap and support their own head more (not entirely), focus their eyes better, and lift their torso up with their arms during tummy time.


Things to consider:
  • At around three-months-old your baby may be able to sustain longer sleeps overnight. Ensuring they’re comfortable in their sleep environment, and establishing a good pre-bed routine can help with this.


  • Need to go back to work? You might start to look into daycare options. It’s normal to feel anxious about this, mama. Look around at a few to find one with the right vibes.


  • DIY baby development chart. While your paediatrician won’t be tracking your baby’s development week by week, that doesn’t mean you don’t have to! It can be cute to keep a journal of all their milestones and achievements so you don’t forget these precious moments.

4-6 months old

Baby growth at 4–6 months

By five months old, your baby will probably have doubled their birth weight. As they prepare to start eating solid foods, get ready for their growth to really take off over the coming months!

Baby development at 4-6 months

Your little one will pick up lots of new skills over these few months. At your scheduled baby development checkups, your healthcare practitioner will look out for key baby development milestones.

At four months your baby may be able to:

  • Roll from their tummy to their back.
  • Push down on their legs when feet are on a hard surface.
  • Hold their head unsupported.
  • Recognize familiar people at a distance
  • Reach out for toys.
  • Copy sounds and facial expressions.
  • Do lots of smiling.

At six months, they may be able to:

  • Get worried when looking at a stranger.
  • Look at themselves in the mirror. (Tiny narcissists!)
  • Respond to their name.
  • Make more distinct sounds. (‘Bah’, ‘Gah’)
  • Put things in their mouth.
  • Transfer objects from one hand to the other.
  • Roll over.
  • Sit unsupported.

Hell, they may even start crawling at six months. Time to
baby-proof your house.

Things to consider:
  • Start offering solids. The American Academy of Pediatrics notes that as babies develop at different rates, it’s best to look for signs of readiness when starting solids. It’s good to start the process no later than six months, as they’ll need additional iron from food which they can’t get from breast milk.

  • Can’t recall what ‘sleep’ is? Sorry to break it to you, but some babies don’t sleep through the night for months or (*gulp*) even years. Trying a new approach to sleep might help you manage better, but know that mums all over the world can relate to the struggle!

Most babies
start cutting teeth around six months of age. It could happen earlier or later, though.

7-9 months old

Baby growth at 7–9 months

From ages six to 12 months, baby growth tends to slow down a little. They might grow about 1cm (3/8 inch) a month and gain 85-140 grams (about three to five ounces) a week. And they’re likely to triple their birth weight by their first birthday!

Baby development at 7–9 months

Expect your little one to hit some serious baby development milestones during this period. As they get more agency over their bodies and start to move around more, they’ll keep you on your toes for sure!

By nine months, they may have learned to:

  • Get into a sitting position by themselves.
  • Pull themselves up on furniture (or you) to stand.
  • Crawl. (Yikes.)
  • Pick things up between their thumb and forefinger.
  • Understand object permanence (and look for things you hide).
  • Play peek-a-boo.
  • Understand “no” (whether or not they obey it is another matter…)
  • Point at things.
  • Have favourite toys.
  • Make lots of sounds, and maybe even make some simple words like, ‘mama’, ‘dada’.
  • Be clingy with their favourite adults. 

Things to consider:
  • Start actively teaching your child. They understand SO much more than we know. Using play and language to teach concepts like ‘hot’ and ‘cold, or ‘happy’ and ‘sad’ can begin at any time. Remember, your baby learns so much from you, even if you don’t consider yourself (technically) an educator.

  • Talk to them. While your baby may not be speaking yet, they’re processing the things you say. Narrating what you’re doing out loud can help them understand words and concepts well before they’re talking about them.

  • Encourage your child to eat and drink independently. At around eight months babies start to get the hang of using their hands to drink from a cup or use a spoon. It might be messy for a while, but embracing the inevitable spills and encouraging them to try can give them a big confidence boost and improve their fine motor skills. Some parents like to wean their babies off the bottle at around this age and teach them to use a sippy cup instead. 

10-12 months old

Baby growth at 10–12 months

At 10 months, the average baby girl will be about 71.5cm (28 inches) in length, and weigh 8.5kg (18.5 pounds). A baby boy will be about 73.3cm (29 inches) long, and weigh 9.2kg (20 pounds).

We’ve said it a billion times already but we’ll say it again: we’re just talking averages here. Your paediatrician will measure your child against their baby development chart to determine if they’re on track for their unique baby growth percentile.

By the time they reach 12 months, they’re expected to have tripled their birth weight and be 50% longer than they were when they slid out of your uterus. They might have anywhere between one and eight teeth by now, too.

Baby development at 10–12 months

During the last few months of your baby’s first year, they’ll be developing in leaps and bounds. But we hope for your sake they’re not actually leaping and bounding yet. Some clumsy walking or crawling is hassle enough, thank you.

By 12 months, babies are measured against developmental milestones such as:

  • Saying a couple of simple words.
  • Understanding and obeying simple instructions.
  • Doing simple actions like waving goodbye.
  • Connecting names and objects.
  • Playing simple games like peek-a-boo.
  • Sitting up unassisted.
  • Taking a few steps, standing alone, or trying to walk by holding onto furniture or your hand.
  • Showing fear in some situations.
  • Being shy or unsure around new people.

Things to consider:
  • Your baby may already be sleeping in their own room, but a lot of parents make the transition after their child turns one. Getting a trusty baby monitor can help relieve any anxiety you have about it – and watching what your baby does to put themselves to sleep can be mighty good entertainment too.

  • Now that your baby is seriously mobile, it’s important to watch out for potential dangers around the house. Lock your valuables away, lest your toddler dump them in the toilet. Ensure chemicals and medicines are stored well out of reach.

  • Plan a birthday party. Your one-year-old probably won’t understand that it’s for them, but let’s be honest – it’s more to celebrate your hard work anyway. Enjoy your their special day, mama.

F*ck. Is this the start of toddlerdom?

At one year old, your doctor will again plot your child’s measurements on a standardised baby growth chart to ensure they’re physically developing in the right pattern. Ensuring they’re eating enough and getting a good level of interaction and stimulation is key to nailing this growth and development thing.

So, now what? Is your kid a toddler? Do you get some kind of medal? Is there an initiation ceremony? 

Making it through the first year is a huge achievement. We know it’s not exactly easy, but holy hell can it be amazing at times. (The first GIGGLE!)

If you thought the first year was fun, just WAIT for their second year. As your child continues to develop, they’ll pick up more independence, language skills, physical ability and amazing, amazing personality. 

It’s so much fun. It’s also super tough work. But you’re up to the task. If you’ve made it this far, you’re doing great! Learn more and connect with other mums on the same wild ride as you by downloading Mumli today.

MedLine Plus, Normal growth and development

Verywell Family, Welcome to Your Baby’s First Year

Raising Children Network, About baby development and developmental milestones

Centers for Disease and Control Prevention, CDC’s Developmental Milestones

Word Health Organization, Child growth standards

Mayo Clinic, How much should I expect my baby to grow in the first year?

The American Academy of Pediatrics, Starting Solid Foods

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