4 Month Old Baby: A Development And Milestones Guide

Your little munchkin is now a “big” 4 month old and is perhaps in one of the most beautiful stages of their young lives. By now, your baby is more expressive, and you will often notice them smiling, cooing, and laughing incessantly. How cute!

Your baby will also see many new physical changes as a new parent.

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 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? Here are a few critical changes you will witness in your 4 month old baby this month.

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

4 Month Old Baby: Physical Development

In the fourth month, your baby’s physical development will be faster than you’ve seen. By now, they should be double their 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 their head steady and unsupported. If your little explorer is super active, you will also see them trying to push their legs down whenever their feet are on a hard surface.

Since your 4-month-old baby is just learning to move more frequently by this time, you’ll be running for your video camera to capture the moment they turn from tummy to back and vice versa. Right now, you’ll see your baby trying to bring their hands to their mouth and even push their elbows up while lying on their tummy. 

At this stage, anything your baby can pick up will likely end up in their mouth. So if you 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 their mouth. 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 be able to focus better on any particularly moving or bright object. This is because their 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 unable to move both eyes together or seems to be cross-eyed, report it to the paediatrician.

How to support your 4 month old’s physical development

• Safety first! Remember to remove sharp jewellery pieces from your ears and even necklaces when you hold your baby. 
• Baby might be turning over on their tummy alone. But if they’re not, continue giving them some tummy time.
• Get a baby gym for your baby. They 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 them sit or stand for long, as it may affect their legs. 
• Provide your baby with many 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 they get hurt. Most importantly, always have your baby close by you (while playing).
• 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.

Consult a doctor if your baby:

• Is not interested in anything. 
• Does not respond to your voice.
• Does not kick or wave their arms.
• Has difficulty turning their head.

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 their fast cognitive development this month.

Your 4 month old baby will also respond to your affections more often. So when you call out to your baby, they may look at you and smile, recognising your affection. 

Also, the baby’s hand and eye coordination will have improved by this time. So this means they will spot objects and reach for them more effectively. Since your baby’s motor skills have developed further, you will also notice them spotting objects and moving their eyes. 

How to promote your 4-month-old’s brain development

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

Consult a doctor if your baby:

• Does not smile at or interact with you or others.
• Does not grab 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 them. 

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

How to nurture your 4 month old’s emotional development

• Your cheeky baby might do things to get a reaction from you, like pulling your hair or gumming/ biting down as they breastfeed. 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 them. 

Consult a doctor if your baby:

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

Your 4 month old cutie is getting very expressive!

Speech and Language Development

As your baby turns four months old, their ability to communicate will heighten, and they will be able to tell you if they are happy or sad more easily. Of course, this won’t be with words yet, but through smiles, coos, or tears.

In trying to understand how your baby may behave or develop, let’s not forget that your little bub will 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 they just heard – although not exactly. The baby may also start babbling now.

How to encourage your 4 month old’s speech and language development:

• 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, they will be able to understand the context and draw parallels between the words and their meaning in the future.

How to nurture your 4 month old’s emotional development

• Is not cooing or making any noise at all. 

Health and Nutrition

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

At this age, baby boys need around 579 calories daily, 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

Your tiny munchkin might have a better, more stable napping schedule by the fourth month. 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.

How to support your 4 month old baby’s health:

• Continue breastfeeding as usual. Ask your doctor if your baby needs Vitamin D supplements. 
• Despite what they might tell you, do not allow other baby carers to feed them solids yet. 

Vaccination and Common Illnesses

At this age, your baby will receive their second dose of 5 in 1, the second dose of the Rotavirus vaccine, and the first dose of PCV. 

While your little one is more robust than a few months ago, their immune system is still immature. This, combined with an incomplete vaccination schedule, makes them 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, soles, 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, they could lead to severe consequences in a young baby.

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

Treating Common Illnesses 

If your little one gets a cold or other common illness, you should immediately bring them to the paediatrician. At 4 months old, your baby is too young for home remedies. 

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

A few reminders:

• Ask your paediatrician about giving your baby the flu shot. 
• Keep following safe sleep guidelines, which include placing the baby down on his back to sleep and removing all bedding and toys from the cot. 

Consult a doctor if your baby:

• Is not growing according to their percentile, or if they fall below the 5th percentile for their 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.

Image Source: iStock

4 Month Old Sleep Schedule

A 4-month-old baby needs between 12 and 17 hours of sleep each day.

Babies need to sleep for different amounts of time at this age, depending on their development. Some babies may need more than others, but a good rule of thumb is that your baby will sleep for about the same time as they do in their crib. If they’re only napping for 20 minutes, then they’re probably not getting enough sleep at night.

You can start helping your baby develop good sleeping habits by putting her to bed when they’re tired and waking them up when they are rested. If your baby wakes up at night and cries, you should hold them until they fall asleep.

Your 4-month-old’s sleep schedule is about meeting their needs and learning from you.

They probably won’t be happy if they’re not getting enough sleep. They’ll fuss and cry and be grumpy at night. And if they’re getting too much sleep, it can make for an unhappy baby—they might cry when awakened or even startle awake in the middle of the night.

You want to make sure that your 4-month-old is getting enough sleep—and not too much of it. Here are some things to think about as you figure out what works best for your baby:

• When do they usually go to bed?
• What time do you usually put them down for naps?
• How long do their naps last?
• How many total hours of sleep do they get each day?

How Much Milk Should a 4 Month Old Drink

The answer is: it depends. A lot!

Infants are growing like crazy, and they need lots of calories to support that growth. Breast milk or formula helps supply those calories. But what’s the right amount?

The answer is: it depends on how often your baby eats. It’s recommended that babies drink from 4 to 6 ounces (120–180 milliliters) at each feeding, depending on how often they eat. So if you’re feeding your baby every three hours, you’ll want to aim for at least 16 ounces per day—and that’s on top of any snacks you give them between meals!

This may sound like a lot, but remember: these recommendations are just a starting point—you can adjust as needed based on how your little one is doing. If they seem hungry after eating less than four ounces, add more! And if they seem satisfied after eating more than six ounces, stop there!

If you have any questions regarding your 4 month old baby’s weight, health and development, do not hesitate to consult your child’s paediatrician.

Image Source: Shutterstock

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

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

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

Updates from Pheona Ilagan

Here at theAsianparent Singapore, it’s important for us to give information that is correct, significant, and timely. But this doesn’t serve as an alternative for medical advice or medical treatment. theAsianparent Singapore is not responsible for those that would choose to drink medicines based on information from our website. If you have any doubts, we recommend consulting your doctor for clearer information.