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Your baby's growth and development - 4 months old

7-minute read

Key facts

  • 4 month old babies can pick up objects with their fingers and thumb, and will try to put their hands (and objects they hold) in their mouths.
  • By 4 months, many babies can chuckle and show delight or excitement.
  • They can also show emotions like anger and frustration, and they might whinge rather than cry at times.
  • Most babies have doubled their birth weight by the time they reach 4 months of age.
  • Your baby is now due for their next round of vaccinations, which will be the same as their first round: 2 injections and the oral rotavirus vaccine.

My 4 month old

From 4 months, your baby will quickly be learning to coordinate their body. They will have more control over what they do, their vision, touch and hearing will be much more developed, and they will start to move around much more. They can communicate much better too, and the amount of time they spend crying should have settled by now.

Your baby will still be gaining weight steadily — probably about 0.45kg to 0.56kg a month. Most babies have doubled their birth weight by the time they reach 4 months of age. Their bones will be growing fast and they will be getting longer.

Along with their physical growth, 4 month old babies are learning more about their place in the world. They will be starting to show an interest in solid food and many of their new skills are preparing them for chewing.

Your baby is now due for their next round of vaccinations which will be the same as their first round: 2 injections and the oral rotavirus vaccine. Your child may be offered an additional injection if they are Aboriginal and Torres Strait Islander, or they have certain medical conditions.

Understanding baby growth charts

Understanding baby growth charts

A growth chart helps you and your doctor keep track of how your baby is growing.

What can my baby do?

Physical development

Your 4 month old will pick up objects with their fingers and thumb and will try to put their hands (and everything else!) in their mouth. This is normal and they are teaching their mouth new skills, as well as getting ready for solid food. Just be careful they don’t put anything small enough to fit inside their mouth completely, to avoid the risk of choking.

From 4 months of age, your baby's physical skills will really start to develop more noticeably. They will soon be rolling over, sitting up and some may even start crawling in the next few months (though most babies start crawling at around 9 months).

Cognitive development

Your baby’s eyesight will be really improving and they will start to link what they see to what they hear, taste and feel.

Social development

Now you can really start to have fun with your baby. You can look into each other’s eyes, smile at each other, laugh and ‘talk’.

Emotional development

Babies at this age love looking at themselves in the mirror and might smile and talk to their reflection. Babies this age can also chuckle and show delight or excitement. They can also show emotions like anger and frustration and might whinge at times, rather than crying. You will get to learn your baby’s cues for being hungry or tired so you can respond to them.

Language development

By 4 months, many babies will try to copy sounds like, saying ‘ah-goo’ and squealing. They might even say ‘ma-ma’ or ‘da-da’ but don’t get too excited — they probably don’t connect these words with you.

How can I help my baby develop?

Keep on talking and reading to your baby to help them learn about language and communication. Use different tones and intonations in your voice, or different facial expressions to emphasise the story.

Your baby will love singing songs, reading books, playing with toys and listening to you making funny sounds.

It will help your baby if you develop a routine. If it works for both of you, do things in a similar pattern each day. This will help them to feel safe and secure.

It’s also a good idea to think about preparing your home for when they start moving around. It could happen soon!

Development problem signs

All babies develop at different rates.

At 4 months, talk to your doctor or maternal child health nurse if they:

  • don’t seem interested in things around them
  • don’t seem to know you
  • aren’t making any voice sounds
  • don’t open their fingers
  • don’t kick their legs, or their legs are bent most of the time
  • don’t follow an object with their eyes or make eye contact
  • don’t turn when you speak to them, or they aren’t startled by a loud noise
  • are unhappy or unsettled most of the time

Resources and support

If you are worried or would like to discuss any issues with your baby’s development, speak to your doctor or child health nurse.

Speak to a maternal child health nurse

Call Pregnancy, Birth and Baby to speak to a maternal child health nurse on 1800 882 436 or video call. Available 7am to midnight (AET), 7 days a week.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: December 2022


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Need more information?

Child's development birth to 4 months | StartingBlocks.gov.au

Information to encourage your baby’s learning and development from birth.

Read more on Starting Blocks website

Your baby's growth and development - 5 months old

At 5 months, your baby is growing and developing quickly. They may soon sit on their own, prepare for solid foods and language skills.

Read more on Pregnancy, Birth & Baby website

Baby language development: 3-12 months | Raising Children Network

At 3-12 months, there’s a lot happening with baby language development. Expect your baby to coo, laugh, play with sounds, babble and gesture. Read more.

Read more on raisingchildren.net.au website

Growth and development for premature babies

Premature babies have a higher chance of having problems with their growth and development. The earlier your baby is born, the higher their chance is.

Read more on Pregnancy, Birth & Baby website

Understanding baby growth charts

Baby (or infant) growth charts indicate how your baby is growing. They record changes in your baby's length, weight, and head circumference.

Read more on Pregnancy, Birth & Baby website

How your baby gains weight

All babies gain weight at different rates. Understand your baby's healthy weight gain with guidelines on feeding, growth and developmental milestones.

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Routine health checks for babies and children

Routine health checks with a child health nurse or GP will check your child's growth and development and keep up to date with their routine vaccinations.

Read more on Pregnancy, Birth & Baby website

Tooth arrival chart

Babies are usually born with 20 baby teeth. Use this chart to see when you can expect their teeth to come through.

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Slow weight gain

Slow weight gain, previously known as 'failure to thrive’, is when a baby doesn’t grow as expected. Learn about why it happens and what to do.

Read more on Pregnancy, Birth & Baby website

Balancing introducing solids with milk feeds

A balanced diet is important for your baby’s development. Learn about introducing solids to your baby’s diet and while maintaining milk feeds.

Read more on Pregnancy, Birth & Baby website

Call us and speak to a Maternal Child Health Nurse for personal advice and guidance.

Need further advice or guidance from our maternal child health nurses?

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This information is for your general information and use only and is not intended to be used as medical advice and should not be used to diagnose, treat, cure or prevent any medical condition, nor should it be used for therapeutic purposes.

The information is not a substitute for independent professional advice and should not be used as an alternative to professional health care. If you have a particular medical problem, please consult a healthcare professional.

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