4 month old baby milestones: Development, growth, speech, language, and more

Babies at 4 months are working on exciting skills as they learn and grow every day. At this age, they’re learning to interact with people and objects in new ways by smiling, cooing, reaching for toys and putting them in their mouth, and more. 

In this article, we’ll cover what to expect when it comes to 17 - 21 week old babies, provide you with a handy 4 month old development checklist, and provide useful tips to help ensure your little one is reaching appropriate milestones.   

IN THIS ARTICLE: 

4 month old baby milestones at a glance

4 month development milestones

17 to 21 week old development milestones checklist

5 development tips for 4 months

Takeaway: Development milestones for 4 month olds

17 - 21 week old developmental milestones FAQ

4 month old baby milestones at a glance

Development:

4 month olds are working on exploring the world in their own ways. Between 4 - 5 months, they’re usually able to reach and grab items and then bring them to their mouth, which gives them exciting new sensory information. They’re also getting stronger thanks to tummy time and floor play, which will help set them up for success with future motor milestones like rolling and sitting up. 

Little ones are also working on their communication skills between 17 - 21 weeks. They’re likely turning towards sounds, like a familiar person’s voice, and offering up adorable coos and smiles when they’re content. If they’re not happy, they might be trying to let you know what’s wrong at this age by changing up their cry to indicate different needs. 

Sleep:

We recommend aiming for about 14.5 hours of total sleep in a 24-hour period. This usually includes 3.5 - 4.5 hours of daytime sleep split up into 3 - 4 naps. If your little one is taking longer naps, they may do well with a 3-nap schedule. Your baby will likely take 4 naps per day if their naps are on the shorter side. If this is the case, try not to feel discouraged by short spurts of daytime sleep. It’s common to see 30 - 45 minute naps at this age. 

Note that these recommendations are general guidelines and monitoring your child’s energy levels and mood is also important when it comes to making sure your baby is getting enough sleep. Some children have higher or lower sleep needs, so don’t stress about the overall number if your baby seems well-rested.

You may also be wondering about the dreaded “4 month sleep regression.” Interestingly, it isn’t really a regression at all. It’s a period of development and a biological change in a baby’s stages and cycles of sleep. At around 4 months, babies begin to have additional cycles of light sleep and deep sleep, similar to an adult. This is a sign of maturation instead of a temporary phase to get past. 

While this change happens for all babies, it may not always negatively impact sleep. However, some signs of the 4 month sleep regression can include sudden worsening of night sleep, increased fussiness at sleep times and a harder time settling for sleep, disrupted naps and less daytime sleep, and distracted daytime eating. If your baby is experiencing any of these symptoms, you’re not alone! 

Your baby might start sleeping better if they follow an age-appropriate 4 month old sleep schedule, can developmentally link sleep cycles, and learn how to fall asleep independently. Consider submitting for a sleep plan through Huckleberry Premium if you’d like step-by-step guidance tailored to you and your baby.

Feeding: 

Your baby should still meet all their nutritional needs with breast milk and/or formula at 4 months old. They may signal that they’re hungry by putting their hands near their mouth [1]. 

Solids are on the horizon! However, the American Academy of Pediatrics [2] advises waiting until 6 months of age to start giving your baby solid foods. Between 17 - 21 weeks, your little one may be showing interest in the foods you eat and working on the skills necessary to start eating solids [3] — like being able to sit in a high chair with good head control, bringing objects to their mouth, and trying to grab small objects. 

Growth: 

Between 4 - 6 months, most babies gain an average of 1 to 1.25 pounds per month. Around 4 - 5 months, their birth weight has usually doubled [4]! On average, a baby will also grow .5 - 1 inch in height between 17 - 21 weeks. Their head will likely grow around .5 inches too. 

Keep in mind your baby may grow more or less than this over the course of a month. That’s normal! Your child’s doctor will check that they’re growing at a regular pace by plotting their height and weight on a growth chart at every visit. That way, they can quickly pinpoint any trends that need attention. Bring up any concerns you may have about your baby’s growth and development with their pediatrician. 

4 month development milestones

Physical development

Gross motor skills 

Head control: An expected 4 month gross motor milestone is the ability to hold their head steady without support while being held. 

Rolling: Around 4 months your baby may start to roll over. Little ones typically roll from their tummy to their back first. Sometimes this happens by accident when a baby is doing tummy time and the weight of their head causes them to roll over. At 4 months this may be happening more intentionally as well. 

Often a baby will practice rolling from their tummy to back for a month or two [5] before being able to roll from their back to tummy. By around 6 months [4], most little ones are able to roll both ways. 

Tummy time: Your little one is getting to be a tummy time pro at 4 months [6]! At this age, most babies are able to lift their heads up 90 degrees while doing tummy time and maintain a centered position thanks to increased neck strength. They can usually also push up onto their forearms with their chest lifted and their elbows beneath their shoulders. These skills allow curious 4 month olds to track toys, faces, and sounds while spending time on their belly. 

Fine motor skills

Reaching and grabbing: 4 month fine motor milestones mean your baby likely has busy hands! At this age, they’re often reaching and grabbing [7] at everything — toys, blocks, dangling items, etc. They’re also working on holding onto a toy when you put it in their hand. 

Hands to mouth: Babies are usually able to bring their hands to their mouth [1] at this stage due to improving hand-eye coordination. They often chomp on their fingers and anything that’s placed in their hands! Because of this, be sure to keep small objects that could be choking hazards out of reach. 

Social development

Smiles and laughs: Get those cameras ready — your baby at 4 months is likely smiling on their own [8] to get your attention. And they’ll probably continue “asking” for attention by looking at you, moving, or making sounds. How cute is that? They’re probably also starting to chuckle at this age, but probably not fully laughing quite yet.

Cries: 4 month old emotional development often means they will use their cries to help differentiate their needs. Cries at this age will start to sound different [1], depending on if they’re tired, hungry, or possibly in pain. 

Speech development 

Cooing: Expect to hear some adorable new sounds [1] from your 4 month old. They may make cooing sounds like “ooo” and “ahh” at this age. They might even “respond” to you with sweet sounds when you talk to them.

Attention to sound: Infants at 4 months can typically turn their heads towards the sound [8] of your voice. 

17 to 21 week old development milestones checklist

Most babies will hit the following milestones by 17 - 21 weeks, though this might not always be the case. Little ones learn and grow at different rates and there’s a wide spectrum of normal when it comes to development. However, if you notice any red flags or potential delays in 4 month developmental milestones, consider consulting with their healthcare provider. 

• Hold head steady without support 

• May roll tummy to back 

• Lift head up 90 degrees while doing tummy time

• Reach and grab objects

• Hold a toy placed in their hands

• Bring hands to mouth 

• Smile to get your attention 

• Cry to indicate different needs 

• Make cooing sounds like “ooo” and “aah”

• Turn their head towards sounds 

5 development tips for 4 months

Tip #1: Smile and chat with your baby 

While your little one won’t understand the words you’re saying for quite some time, you can help lay the foundation for their language development by smiling and interacting with them. Make it fun! This teaches them [8] about back-and-forth conversations and your happy demeanor can encourage your baby to continue engaging and responding with their own sounds too.  

Tip #2: Get mouthy 

Babies are discovering the world at this age. They’re starting to put everything in their mouth — that’s how they explore! While it can be stressful for parents, exploring through touch and taste [9] is key for your little one’s brain development. Just be sure to keep anything that’s sharp, hot, or small enough to choke on far out of reach.

Tip #3: Read books with big, bright pictures

At 4 months, babies tend to like looking at bright patterns and color variations [4] as their vision develops. Your child will likely enjoy reading books with large, bright objects for them to look at. Try pointing out and naming the things you see in the book and narrating what’s happening to boost their thought and speech development [8] too.  

Tip #4: Say my name

You probably have a whole list of cute nicknames for your baby and that’s great! Try to call them by their name too to help them learn it. One study [10] showed that babies recognize the sound pattern of their own name as early as 4.5 months! 

Tip #5: Tummy time  

Help your baby move, learn, and explore by having them spend plenty of time on the floor and their tummy daily. Aim for about 90 minutes total [11] of tummy time per day for 4 month olds. Tummy time helps strengthen the back, arm, and neck muscles needed for upcoming motor skills like rolling and sitting up.

Spending time on the floor [12] also increases their independence and confidence. Note that you should always closely supervise your baby during these activities, but you can start to give them the ability to play and problem-solve on their own.  

Takeaway: Development milestones for 4 month olds

• It’s so exciting to watch your child learn and grow between 4 - 5 months! At this age, your little one is likely holding their head steady without support and working on strengthening their muscles during tummy time each day. They may even start rolling from tummy to back this month. 

• 4 month milestones for the baby also include reaching and grabbing for all sorts of toys and objects and then likely bringing these items to their mouth. Mouthing helps babies learn about the world! 

• 4 month old speech milestones include big smiles and cute coos! Expect your baby to start making “ooo” and “ahh” noises around 17 - 21 weeks. They will also likely turn towards the sound of your voice at this stage.

• There’s a wide spectrum of normal when it comes to 4 month old milestones. It’s normal if your little one isn’t doing all of these things between 17 - 21 weeks as babies reach milestones at different times. That said, if you notice any 4 month old milestone red flags or delays, check in with your child’s healthcare provider.

If you're curious about what lies ahead in the coming month, glimpse into the future to see what you might experience once your baby is 5 months old.