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4 Month Old Baby Milestones & Development

4 Month Old Baby Facts

At 4 months old, your baby is a bundle of rapidly developing social joy, just waiting to break out of that limited physical movement and make their first real social bonds and contacts. They’re going to be more social in month 4 than ever before, as the arrival of 4 month old baby milestones land on your doorstep and melt your heart. The little things will mean a lot at this age, as they’re not fully mobile yet, and won’t be, but you will notice more movement than ever before.

Physical Growth

The physical growth of babies at 4 months old continues unabated, hopefully, and should culminate in final weight totals of 10 to 19 pounds for girls and 11 to 20 pounds for boys. Height should be around 22 and 26.5 inches for girls and 23 and 27 inches for boys. While boys are slightly larger, it’s not unusual for some girls to be bigger than some boys or vice versa. The entire first year is completely covered in growth spurts and changing sizes, something some parents may find overwhelming to keep up with when shopping for clothes. It’s a small price to pay for a healthy and growing baby, though.


When those 4 month old baby milestones arrive, your baby should be feeding 5 to 6 times a day (if you breastfeed) or 5 times a day for formula feedings. 24 to 36 ounces of formula a day, or breastmilk, will be what your average 4 month old baby is feeding on during that 4th month. These feeding times are important for bonding with your little one, but you’ll also notice your little one is more curious about the world around them, too. What else are these little critters up to in terms of 4 month old baby milestones? Let’s find out!

1. Baby rolls over

4 months is generally the age where you’ve got to be careful about putting blankets in the crib or sleeping area. Why? Well, it’s at this age that rolling over joins the ranks of 4 month old baby milestones. At this age, your baby is able to roll over from their front to their back. Once a baby is able to turn over, things that can cover their face become hazardous in the crib or sleeping area, so it’s usually at this age that swaddling might be something to do only when it’s supervised. Your baby can also do a host of other neat things, such as put their fist in their mouth and follow objects from side to side with their eyes. They’re watching the world in a way they never have before, and you’re the lucky witness.

2. Sits with support

Your care and support will help your baby reach 4 month old baby milestones more quickly. For example, with your support, a baby can usually sit up for a bit at 4 months old. Your support helps to strength the back, shoulder, and hand muscles that will one day play a part in your baby sitting up on their own. A lot of muscle development takes place to make these small miracles possible, and if you help your baby sit up with support at 4 months, it’s going to build those all important muscles to aid them in sitting up on their own later on. Keep at it!

3. Spontaneous smiling

Getting your younger baby to smile can be a real work of art, and take a lot of time, but at 4 months old, they reach 4 month old baby milestones like learning how to smile on their own, out of the blue. Imagine holding a toy up in front of your baby’s eyes, and suddenly a big old smile bursts forward, their eyes twinkling, a happy glow. Those are the kinds of things you have to look forward to with 4 month old baby milestones! They’re just now at the point and time where they not only perceive their environment, but they can interact happily with it, and you. It’s a huge bonding moment between parents and baby.

4. Let the mimicking begin

Your facial expressions are one of the first cues your baby gets from the environment. When you look at them and smile, their little brains are taking everything in, but until month 4, they’re not quite able to interact with you in this way just yet. One of the most adorable 4 month old baby milestones is that moment where your baby can see your facial expressions and then mimic them. If you smile, they might smile. If you frown, they might frown right back at you. It’s one of those smile-inducing moments all the way around for a baby and their parents. Your child is learning from you with this 4 month old baby milestones moment.

5. Holding objects

Another terrific 4 month old baby milestones moment is when you little one grabs an object and holds it. It could be something like a toy (a baby rattle) or another object that they see such as a pacifier. The idea that your baby can hold onto objects and keep them in their possession is a true accomplishment. For us, this is second nature, but to them it’s an achievement of coordination and muscle development that really hammers home just how much your little one is growing up. Sure, they’re not quite ready for college yet, but your little one is learning all the skills they need in life, including the ability to hold an object.

Cherish Milestones

Your baby’s 4 month old baby milestones are uniquely theirs. No two babies get the same abilities on the same day, in the same order, in the same way. Some babies will master the art of mimicking your expressions instantly at 4 months old, while others won’t get the hang of this for another month or two. Some may even develop these gifts a bit early. What’s important is that your child is developing in a healthy, wondrous way that you can share with others.

Taking pictures of those 4 month old baby milestones will cement them in memory and allow you to share them with your child later on.

Photographable Milestones

  • Mimicked smiles
  • The first rattle they held in their hand
  • A roll over moment
  • Cute baby side to side eye moment captures

Each one of these moments is something you’ll always remember with your child, and let’s face it, they’re fun to share on social media, too. Don’t get so caught up in the pictures that you miss out on the moment’s, though. Sharing facial expressions with your eager to mimic and learn baby will prove a lot of fun, and sometimes it’s time to put the camera down and simply relish these moments with them. Babies at this age love to be cuddled and talked to as well, along with a host of other parent-baby bonding moments that will cement your bond.

By 4 months, you’ve won over the heart of your little one. They depend on you for all their needs, but by now, they’re starting to really love you, too! Okay, they didn’t just now start the love, but it’s at this age that they’re able to share more of their amazing world with you. They don’t just see your smiles. They return those smiles now, and many other facial expressions they might try to mimic over the years. Your 4 month old baby milestones are increasing everyday, and there’s so many more that could be written about here.


4 months old is a time of major development. You’re going to notice your baby doing so many things that once they struggled to do or didn’t do at all. You’re sharing more of yourself now than ever, as they’ve learned to coo a bit and return your sounds with sounds of their own. They’re getting better at everything from grasping objects to holding them to rolling over from front to back. It’s a constant stage of growth and social interaction that parents and baby alike are going to cherish forever. Don’t miss out on a single moment!

1 thought on “4 Month Old Baby Milestones & Development”

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