Baby development and milestones: your 4 month old

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.

Your little munchkin is now a “big” 4 month oldand is perhaps in one of the most beautiful stage of his/her young life. By now your baby is more expressive, and you will often notice him/her smiling, cooing, and laughing incessantly. How cute!

As a new parent, you will also see many new physical changes in your baby.

By the fourth month, your baby has an adorable layer of fat, and you probably won’t be able to stop yourself from pulling those chubby cheeks. But this is also a time when you’ll have to prepare yourself for an emotional rollercoaster – so much so that the joy and pride your baby will give you will have you reaching for the tissues.

What is going to happen, you ask? Well, here are a few critical changes you will witness in your bub this month.

4 Month Old Development and Milestones: Is Your Baby on Track? 

4 month old

Physical Development

In the fourth month, your baby’s physical development will be faster than you’ve seen so far. By now, he/she should be double his/her birth weight.

At this stage, your child’s median length and weight* should be as follows: 

  • Boys
    – Length: 64.0 cm (25.2 inches)
    – Weight: 7.0 kg (15.4 lb)
  • Girls 
    – Length: 62.2 cm (24.5 inches)
    – Weight: 6.6 kg (14.6 lb)

And your child’s head circumference* should be:

  • Boys: 41.6 cm (16.4 inches)
  • Girls: 40.6 cm (16.0 inches)

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

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

At this stage, anything that your baby can pick up will likely end up in his/her 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/her 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 oldbabies 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/her vision is now 20/40. Your baby will also be able to pick up colours and contrast. So if you notice that your baby is still not able to move both eyes together or seems to be cross-eyed, report it to the paediatrician.


  • Safety first! Remember when you hold your baby, to remove sharp jewellery pieces from your ears and even necklaces. 
  • Baby might be turning over on his/her tummy alone. But if he/she is not, continue giving him/her some tummy time.
  • Get a baby gym for your baby. He/she will enjoy the various sensory stimuli it provides. Your baby may want to sit up or stand with your support. However, make sure not to make him/her sit or stand for long, as it may affect his/her legs. 
  • Provide your baby with lots of textures to explore such as books and soft toys. Just make sure the item is not too small for your baby to swallow and not too big that he/she gets hurt. Most importantly, have your baby 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 interested by anything. 
  • Does not respond to your voice.
  • Does not kick or wave his/her arms.
  • Has difficulty in turning his/her head.
4 month old

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

Cognitive Development

While you notice all these physical changes in your baby, you’ll also be surprised to notice his/her fast cognitive development this month.

Your 4 month oldbaby will also respond to your affections more often. So when you call out to your baby, he/she may look at you and smile, in recognition of your affection. 

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


  • Play peek-a-boo with your 4 month oldbaby and watch those adorable giggles bubble out!
  • Engage your baby’s senses as much as you can. Call out to him/her from different corners of the room.
  • Read books full of shapes and colours to your baby.
  • Take baby 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, the smiles will be more frequent now. 

But a response to your emotions and a heightened ability to express also come with their fair share of tears. For example, If you love playing with your baby and suddenly stop, you may upset him/her. 

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


  • Your cheeky baby might do things to get a reaction from you, like pulling your hair or gumming/ biting down as he/she 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 oldbaby as you read or sing to him/her. 

When to See a Doctor:

If your baby: 

  • Shows no reaction (happy/sad/anxious) to new faces. 
4 month old

Your 4 month oldcutie is getting very expressive!

Speech and Language Development

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

In trying to understand how your baby 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/she just heard – although not exactly. Baby may also start babbling 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/she will 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

In terms of food, your baby still only needs breastmilk which adapts month by month to suit your baby’s nutritional needs.  If you’re not breastfeeding, then formula milk is the only other suitable food for your baby. 

At this age, baby boys need around 579 calories a day, and baby girls need 543.4. Typically, the amount of breastmilk/formula milk for your baby at this stage is:

  • Breastmilk: 19.3-30.4 ounces/day
  • Formula: 25 ounces/day

By the 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 your cherub sleeping for a minimum of 12 to 13 hours per day.


  • 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. 

Vaccination and Common Illnesses

At this age, your baby is going to receive his/her second dose of 5 in 1, the second dose of Rotavirus vaccine, and the first dose of PCV. For more details, to check on future vaccinations and if your baby’s schedule is up-to-date, click this link

While your little one is definitely more robust than a few months ago, his/her immune system is still immature. This combined with an incomplete vaccination schedule makes him/her vulnerable to common illnesses like colds and coughs. Other common illnesses are: 

  • Respiratory Syncytial virus, which has symptoms like runny nose, nasal congestion, and heavy breathing 
  • Hand, Foot and Mouth Disease, which may present itself via fever and sore throat, with some rashes on the palms, sole, trunk and diaper area.
  • Scarlet fever, which has symptoms including a sore throat and red rash around the neck and face. 

While these conditions may not be a big deal in an older child, in a young baby it could lead to severe consequences.

This is why it’s crucial you and all others who handle your baby practice strict hygiene, that must include frequent hand-washing. Wear a mask if you have a cold or cough, and any other family members or friends with colds or who are sick should stay far away from baby until they are better. 

Nobody should ever kiss your baby on his/her face, mouth, hands or feet as this could potentially transmit the fatal HPV virus to your little one. 

Treating Common Illnesses 

In the event your little one gets a cold or and other common illness, you should bring him/her to the paediatrician immediately. At 4 months old, your baby is too young for any kind of home remedies. 

Note: Never give your baby medicine that is not prescribed by a paediatrician.


  • 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/her 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.

*Disclaimer: This is the median length and weight, and head circumference according to WHO standards.

Source: Web MD

Previous month: Baby development and milestones: Your 3-month-old

Next month: Baby development and milestones: Your 5-month-old

Got a parenting concern? Read articles or ask away and get instant answers on our app. Download theAsianparent Community on iOS or Android now!

Written by


app info
get app banner