Ultimate Guide to Your 4 Month Old Baby: Milestones, Growth, Sleep, Development, Poop, and More!

Ultimate Guide to Your 4 Month Old Baby

Congratulations! You’ve made it through the newborn days, and you now have a 4-month-old baby. A baby at this age can become really fun as they become more aware of the world around them, and you get to know their personality a bit more. But, they can also go through some big changes! These changes can impact how they interact with you, how they sleep, how they poop, their feeding schedule, and so much more! Read on to learn more about your 4-month-old baby.

4-Month Old Developmental Milestones

Your 4-month old baby is likely making different facial expressions and learning how to use their hands a bit more. Many babies this age explore their fingers and hands during waking hours and some (not all) begin to use them for self-soothing while they are sleeping. Babies are very curious about things around them and will grab almost anything nearby. This is about the time I stopped wearing earrings. 😉 Babies this age can also hold up their heads better and sit with support a lot of the time. Your baby can likely track items with their eyes, now, too. The most fun part is your 4-month old is likely smiling and possibly even laughing at you (or with you)! Some babies this age are also learning how to roll one way. However, keep in mind that it often takes several weeks/months to roll both ways. Offering ample tummy time is helpful! My sons didn’t always like it, and likely a reason they took quite a long time to crawl (don’t worry — they will!). Rolling over in their sleep is usually the most frustrating stage in this rolling business, but otherwise, some babies can get around with this basic skill and can reach toys a bit out of reach.

Your Baby’s Growth

How much should your 4-month old baby weigh at this point? How long should they be? Should you be worried about your baby’s growth? First and foremost, your baby’s pediatrician will let you know whether you need to be concerned about their physical development. If your baby’s weight and length are staying on their growth curve, even if it’s at a lower percentile, most likely you have no reason to worry. Do keep in contact with your pediatrician or health nurse if you have any concerns at all. According to the WHO growth charts, your 4-month-old baby will likely weigh around 15 pounds for boys and 14 pounds for girls, on average, and be around 21 inches long if they are in the 50th percentile. Keep in mind that the #1 most important thing is that your baby stays on their own growth curve (i.e. if they started on the 15th percentile, they should stay on that percentile or go up, not down). While some do fluctuate a tiny bit, your baby should stay on this curve until they stop tracking it so closely (or, again, go up). It is not necessarily “bad” if your baby is “only” in the 10th percentile.

Premature 4-month-olds

If your baby was born 4 weeks early (or more), then it’s very likely you need to use his or her adjusted age when you consider developmental milestones. Sleep-wise, we tend to see premature babies track somewhere between their actual and adjusted ages. All babies develop on their unique timeline and premature babies are not an exception. In some areas, your baby may be ahead or behind, or right on target, but in other areas, it could be the opposite. I like to think that all babies develop what interests them most first because they are simply trying really hard in that area. My first son loved sign language because he had a lot to say (and still does!), but his younger brother was never interested and thus only learned a few signs to get by (and he still is a young man of few words!). In the end, unless there is a developmental delay, try not to compare your baby with others too much (even their own siblings!). Your healthcare provider will tell you if you need to be concerned.

Sleep Needs and The 4-Month-Sleep Regression

At 4 months old, your baby will need around 11-12 hours of sleep at night and 3-4 hours during the day, on average, for a total of about 16 hours of sleep in a 24-hour period. Of course, if your baby doesn’t get 11-12 hours at night, keep in mind that all babies are unique. Some babies will need less sleep and others will need more sleep. These are just averages and it’s important to observe your own baby and keep an eye on your baby’s wake windows. The American Academy of Pediatrics also recommends you continue sharing a room with your baby until at least 6 months old. Although some babies are very happy despite an obvious lack of sleep, most will indicate they need more sleep with their mood and behavior.

Fussy babies tend to be on the clingier side and often need more sleep. If your baby is very fussy during the day, consider shortening the time they’re awake and getting them more sleep. You might be surprised at the happy little guy or gal hiding in there! If your 4-month-old baby is sleep-deprived, it may be due to the fact that their sleep has fundamentally changed. As a newborn, your baby spends a lot of time in deep sleep, but after what we call the 4-month sleep regression, they now cycle in and out of light and deep sleep and go through sleep cycles. If they don’t know how to get themselves back to sleep, they may be waking much more frequently at night. A baby cries quite a bit during this time and this will make you all exhausted!

Keep in mind that your baby will NOT go back to how they slept as a new baby, so it is key to help them learn to sleep in this new way. Many babies will find their own way and others need your help, hence our very popular free e-book, 5 Ways to Help Your Child Sleep Through the Night. Pick up your copy anytime!

Feeding Amounts

Another thing that could be changing at this age is your 4-month old’s feeding schedule. Even if your baby was sleeping through the night without feedings, we sometimes see a night feeding come back around this age. Keep in mind that newborns don’t move around too much, but now your baby may be sitting or rolling, spending more time awake, and generally burning more calories during the day. If you are bottle-feeding, consider seeing if your baby is ready for a larger bottle of breast milk or formula. At this age, I typically see 4-5 oz breastmilk bottles or 6-7 oz formula bottles. Breast milk is more concentrated than formula, so the bottle sizes are smaller. If you are giving a mixture, it will likely fall somewhere between. That said, some babies don’t take large feedings especially if they have reflux.

The #1 thing to consider is that your baby needs a certain number of calories in a 24-hour period. The less they take in during the day, the more they’ll need at night. It’s important to keep your baby on the growth curve (see above). So we don’t want to deprive them of the calories they need. We just want them to get most of them during the day, if possible. 😉 Is your baby ready for solids? Should you start solids? The general consensus is no, not yet. We start solids closer to 6 months old. But, check with your doctor about what’s best for your baby.

Sample 4-month Old Baby Schedule

We have sample sleep schedules for all ages, but here’s one for you to consider trying. Just remember that your baby is unique and may need different nap and bedtimes.

7:00 AMWake and Milk
8:30 AMNap
10:00 AMMilk
11:30 AMNap
1:00 PMMilk
2:00 PMNap
4:00 PMMilk
4:30 PMCatnap
7:00 PMBedtime (asleep by this time)

Need help with naps or want more sample schedules? Consider checking out our e-Book with over 40 sample schedules, Mastering Naps and Schedules.


Did you ever think you would talk about poop as much as we do after we have babies? I have marveled at the 30-minute conversations I’ve had about poop since becoming a mom! But, it is very important stuff since your baby’s poop can alert you to some serious health issues. A baby’s poop can vary in color quite a bit from a breastfed baby’s mustard-colored yellow poop to a more typical brown (and smelly) poop once a baby starts solid foods. If your baby’s poop is red (indicating blood), chalky white (indicating absence of bile), or black (normal for newborns, but after 3 days old can indicate blood in the gastrointestinal tract), call your doctor immediately!

Any other colors are probably just fine, except if it’s bright green and frothy, your baby is likely breastfed and is getting more of the foremilk, instead of the hindmilk, and needs to drain your breast. If your baby isn’t acting like themself, though, they might have a virus. In terms of consistency, baby poop is often looser than ours, so it’s usually nothing to worry about unless it’s just too watery, which could be diarrhea. It’s best to talk to your doctor, so they can check for infections or other health issues that could be causing it. On the flip side, if your baby is straining and the poop is too hard, this indicates constipation.

You may be feeding them too much solid food and/or they are not getting enough liquids. Try to adjust the milk-to-solid feeding balance. If that doesn’t help or you are concerned, definitely talk to your doctor!

Temperament and Personality

Ah, the fun stuff! Your baby is showing more and more of their personality every day, I’m sure. And, so much of it is fun with smiles for almost everyone. But, some of it isn’t so fun, too. Remember when people would ask nature or nurture? Before I had a baby, I thought so much of behavior was nurture…we teach our babies to behave a certain way. Boy was I wrong! I am now a big believer in nature too. My sons were born with so much personality! As they grew up, I kept seeing the same traits, such as being afraid of strangers, and their first reaction to certain situations. For a quick overview, here are your baby’s temperament traits:

Intensity – How strongly he reacts to something (good or bad). Babies that “go from 0 to 60 in a second flat” are very intense!

Persistence – How easily your baby gives up on something such as a toy that’s taken away. Easy-going babies tend to get over things quickly and move on. This is not a bad trait. Very persistent babies don’t give up easily. At all. Again, this isn’t bad either. Just two different types of babies that will approach life in their own ways.

Perceptive-ness – How much your baby notices things around her. Those who hear “she’s so alert!” may have a perceptive baby.

Adaptability – This indicates how easily your baby eases into new situations. These are babies who are also easy-going, crying for very short periods at things they don’t like.

Regularity – This indicates how predictable your baby is. Can you set a clock by his poop schedule or when he wakes up for the day? Those babies are highly regular.

Energy – Do you have a non-stop mover like the Energizer® bunny? If so, your baby is very energetic and will likely remain so for many years to come. Start exercising now, so you can keep up! (I have two of these, so I speak from experience!)

First Reaction – Is your baby’s first reaction often negative? I was amazed how many times my son would say ‘no’ only to say ‘yes’ a few minutes (sometimes seconds) later. His first reaction is often negative and I had to learn not to necessarily accept it as his “final answer.”

Mood – Some babies are soooo happy almost all the time and others are very serious. Serious babies may be hard to get a smile out of (but watch out when they do!).

Want to know more about these traits? If you haven’t read our series about baby temperament, be sure to check it out!

Toys for a 4 Month Old Baby

For the most part, babies are so curious about everything, you don’t really have to buy many toys. So many babies can play with paper that crinkles or other household goods. They don’t know how sophisticated (or not) an item is. So many parents spend hundreds of dollars on toys only to find their baby loves to play with the box. And, some toys can be downright scary!

With that said, we know sometimes you do need to keep babies entertained all.day.long. Having a few toys in your toolbox is a must. Here are some of my favorite toys:

Educational I kid you not! My son learned his ABC’s at a very young age thanks to a learning table we had. Unfortunately, I had a baby so long ago that I cannot find the exact one we had, but I know for sure it helped. He used to love stopping at “O” to emphasize it. He was reading by age 3 and by 5th grade was reading at a 10th-grade level.

By no means am I telling you this to brag, but he used to LOVE to read for HOURS at a very young age and I do think it absolutely impacted his reading comprehension as he got older. So, I think these learning tables CAN work IF your baby is interested.

As I said earlier, I do think babies exercise the muscles they are interested in. If your baby isn’t interested in this type of thing, it may collect dust. You just never know until you try. Here are a couple of great learning tables and toys:

Gross Motor Most babies who like to move will develop their gross motor skills without much prompting. My son wanted to be on his feet from a very early age. He didn’t crawl until 10 months old, but then walked just 3 weeks later. Why be on your hands and knees when you can be on your feet? He later became a runner. Go figure! He would spend hours jumping in his doorway jumper, too. Here are a few toys focused on gross motor skills. OR use something like these to simply give your energetic baby (see above) an outlet:

Teething and General Toys Your baby may or may not be teething, but they start drooling way early! My first baby did get his first tooth at 5 months old, so it is possible. Of course, my best friend’s baby didn’t get his first tooth until after a year old and they weaned from breastfeeding! You just never know and all babies seem to have their own timetable. Regardless, you may want some toys that are fine to go in the mouth, since that’s how so many babies seem to explore:

Fine Motor To develop your baby’s pincer grasp, you will probably want to wait until he or she is a bit older as we don’t want her to choke on anything. Many people wait until their baby is old enough for Cheerios or whole peas. Therefore, I don’t have any toy recommendations for fine motor skills at this age.

Books for your 4-month old Baby

Think it’s too early to start reading? Think again! We started at 4 months old. As my boys became more mobile, they’d sometimes explore their room as I was reading. They’d come to the book to look for a minute, and then keep exploring. Even when you think they aren’t paying attention, they often are (so be careful about adult conversations in the car as they get older ;)). Here are a few favorites:

When to be concerned about your 4-month old baby’s development

I’m a big believer that you know your baby best. If you have a feeling something isn’t quite right, trust your gut and talk to your doctor. And, consider getting a second opinion, if necessary. I have worked with families who just knew something wasn’t quite right. In one case, the baby ended up having a tongue and lip tie after a couple of doctors and lactation consultants didn’t diagnose it. If you feel in your heart of hearts something isn’t right, there might be something wrong and it’s often better to find out sooner rather than later. That said, it’s easy to worry unnecessarily when you have a new baby you’re raising and you don’t want to do it “wrong.” I was there many times! You’re not alone. Remember that all babies will develop on their own timetable. But, if you are finding your baby falling more and more behind as far as what they’re “supposed” to be doing, it doesn’t hurt to check it out with your pediatrician or other specialists. Early intervention is always preferable and you could help your baby get back on track.

Well, there you have it. Hopefully, you’ve learned a lot about your 4-month old!

Sources: www.webmd.com/parenting/baby/baby-development-4-month-old#1 www.cdc.gov/growthcharts/who_charts.htm#The%20WHO%20Growth%20Charts health.clevelandclinic.org/the-color-of-baby-poop-and-what-it-means-infographic pathways.org brightfutures.aap.org/families/Pages/ParentHandouts_English/4MonthVisit_ParentInfo.aspx

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