Month 4

Baby Development and Milestones: Your 4-Month-Old


Your 4-month-old baby is becoming more curious, adventurous, and quite the taster! So here's what you should be prepared for now.

Physical development

In his fourth month, your baby’s physical development will be faster than you’ve seen so far. He should be double his birth weight.

You’ll also notice him trying to keep his head steady, unsupported. If your little explorer is super active, you will also see him trying to push his legs down whenever his feet are on a hard surface.

Since he is just learning to move more frequently by this month, you’ll be running for your video camera to capture the moment he turns from his tummy to his back and vice versa. Right now, you’ll see him trying to bring his hands to his mouth, and even push his elbows up while lying on his tummy. 

At this stage, anything that your baby can pick up will likely end up in his mouth. So if you do have a dangling toy or one that makes noise, rattles, or even lights up, your baby will try to hold on to it, shake, fling it, and put it in his mouth. In fact, you might want to be prepared because it could also be your hair!

Your baby might have also started rolling by now. Some 4 month old babies even get their first tooth! 

By this time, your baby’s eyes will move together and also be able to focus better on any particular moving or bright object. This is because his vision will now reach 20/40. He’ll also be able to pick up colours and contrast. So if you notice that your baby is still not able to move both his eyes together or seems to be cross-eyed, report it to the paediatrician.


  • Safety first! Remember that when you hold your baby, you remove sharp jewellery pieces from your ears and even necklaces. Because if they’re shiny, trust us, he’s going to want to pull it and put it in his mouth. He will do this primarily because he is becoming more dexterous and using more of his hands.  
  • He might be turning over on his tummy on his own, but if he is not, continue giving him some tummy time.
  • Get a baby gym for him. He will enjoy the various sensory stimuli it provides. He may want to sit up or stand with your support. However, make sure not to make him sit or stand for long, as it may cause bowing of his knees.
  • Provide your baby with lots of textures to explore such as books and soft toys. There are chances he might ditch that and pick up a spoon instead, so let him have a wooden one instead. Just make sure the item is not too small for him to swallow and not too big that he hurts himself. Most importantly, have him close by you (while playing) at all times.
  • Start preparing for a baby who is ready to move around the house. You can add gates to stairways, lock the cabinets, and keep wires away from the floor.

When to see a doctor

If your baby: 

  • Is not involved or interested in any of his activities
  • Does not respond to your voice
  • Does not kick or wave his arms
  • Has difficulty in turning his head

src=https://sg content/uploads/sites/12/2018/04/ya lan baby sleep back.jpg Baby development and milestones: your 4 month old

Your little one’s sleep should slowly start getting more stable.

Cognitive Development

While you notice all these physical changes in him, you’ll also be surprised to notice his fast cognitive development during this month.

Your 4 month old baby will also respond to your affections more often. So when you call out to him he may look at you and smile, in recognition or your affection for him. 

Also, his hand and eye coordination will have improved by this time. So this means he will spot objects and reach for them more effectively. Since his motor skills have developed further, you will also notice him spotting an object and moving his eyes along with it. 


  • Play peek-a-boo with your 4 month old baby and watch those adorable giggles bubble out!
  • Engage his senses as much as you can. Call out to him from different corners of the room.
  • Read to him books full of shapes and colours.
  • Take him out on a ride in his stroller! Avoid screentime as much as you can, though!

When to see a doctor

If your baby: 

  • Does not smile at or interact with you or others
  • Does not grab at item or toys

Social and emotional development

As far as your baby’s emotional and social growth is concerned, you’ll be super happy to notice some new developments this month. Since your baby is now old enough to express and respond to emotions, he’ll smile more frequently now. Now, won’t that just make your day?

But a response to your emotions and a heightened ability to express also come with their fair share of tears.

If you love playing with your baby and suddenly stop, you may upset him. But worry not, this is new to him, too. By this age, he will love to play and may let you know when he wishes to stop or continue.

Also, if you make faces at him, don’t be alarmed if he tries to mimic the same. By this cute age, babies tend to imitate what they see. And that includes making funny faces.

After all, he got it from his mama!


  • Your cheeky baby might do things to get a reaction from you, like pulling your hair or gumming/ biting down as he breastfeeds. A firm “no” said in a gentle, calm voice is enough to indicate you’re not happy with this. 
  • Graduate from board books with black and white images, to those with colourful pictures and even noises. 
  • Interact with your 4 month old baby as you read or sing to him. 

When to see a doctor

If your baby: 

  • Shows no reaction (happy/ sad/ anxious) to new faces 

src=https://sg content/uploads/sites/12/2018/03/baby flung from car 2 .jpg Baby development and milestones: your 4 month old

Your 4 month old cutie is getting very expressive! | Image source: Shutterstock

Speech and Language Development

As your baby turns four months old, his abilities to express himself will heighten, he will be able to tell you if he is happy or sad more easily. Of course this won’t be with words yet, but through his smiles and coos, or tears.

In trying to understand how he may behave or develop, let’s not forget that your little bub is going to pick up everything from you.

So when you call your baby “my little munchkin” in that cutesy sing-song voice, know that your baby will try to copy what he just heard – although not exactly. He may also start babbling by now.


  • To encourage your baby’s language skills, try to talk to your little one just as you would with an adult. Research has shown that adopting a sing-song voice is good for babies. It helps them learn how to speak faster.
  • Use complete sentences and proper grammar. Throw in phrases such as “please” and “thank you.” Even if your tot doesn’t fully comprehend their meaning, he’ll be able to understand the context and draw parallels between the words and their meaning in the future.

When to see a doctor

If your child: 

  • Is not cooing or making any noise at all. 

Health and Nutrition

By now, your baby would weigh around 6.2 to 7.8 kgs. His height/ length should be between 58 to 66 cms. That said, there might be variations in a healthy child. So follow his growth using the percentile charts. Ideally, children maintain a percentile growing up. 

In terms of food, your baby still only needs breastmilk which adapts month by month to suit your baby’s nutritional needs.  

By his fourth month, your tiny munchkin might have a better, more stable napping schedule. Typically, a baby sleeps for seven to eight hours by this time. And if you factor in one or two naps, you’ll see him sleeping for a minimum of 12 to 13 hours per day.

At this age, your baby is going to receive his second dose of 5 in 1, his second dose of Rotavirus vaccine, and his first dose of PCV. 


  • Continue breastfeeding as usual. Ask your doctor if your baby needs Vitamin D supplements. 
  • Do not allow other carers of your baby to feed him solids yet, despite what they might tell you. 
  • Ask your paediatrician about giving your baby the flu shot. 
  • Keep following safe sleep guidelines, which include placing baby down on his back to sleep, and removing all bedding and toys from him cot. 

When to see a doctor

If your child: 

  • Is not growing according to his percentile, or if he falls below the 5th percentile for his age. 
  • Is running a fever of 38 degrees Celsius or higher.
  • Has a rash, bruises or suffers a major head-bumping incident. 
  • Vomits very frequently.