By month four, babies are alert and actively reacting to the happenings in their environment. They’re finally ready for interactive play, eager to grab at toys and delight everyone with their ready smiles and laughter. Welcome to the”golden age” of babyhood. The fun is just beginning!

Four-Month-Old Development

If you’re feeling like your baby is growing muy rapido, you’re right. By the end of this month, some babies will have doubled their birth weight. But weight gain does begin to slow down this month, to somewhere between three quarters of a pound and a pound and a half. They’ll continue to add about ½ inch in length and head circumference.

Movement Development

Motor

You’ll notice a lot of exciting, and some challenging, developments this month. It’s a good time to childproof your house  – next month might be a little late, depending on how quickly your child is mobilizing! Start by getting down on the ground to see what’s at baby’s level that he’ll want to put in his mouth.

Getting squirmy

Your baby is likely wiggling and fidgeting a lot, which can make changing diapers difficult! From now until toilet training (so, years), speed and distraction will need to be your diaper-changing MO.
Getting stronger: Put your baby on her tummy and she’ll practice her baby push-ups, putting her weight on her elbows or hands and pushing up. If she’s feeling ambitious, she might even scoot in a circle or project herself a few inches backward or forward. 

Under control

By the middle of this month, most babies can keep their heads steady when held in a sitting position. Kudos to those tiny, strengthening neck and back muscles, giving parents the all-clear to prop baby up on a pillow or adjust the stroller so baby can look around.

Ready, set, roll

Most babies start rolling over this month. Of course, some begin earlier, some later, and some skip rolling over altogether. Those who do make a move will likely flip from belly to back first (it’s easier). Even if your baby isn’t showing any signs of rolling, never leave your baby on an elevated surface – that first roll could happen at any time!

Bouncing baby boys and girls

Toward the end of this month, your baby’s legs will be strong enough to bear his weight. Stand your baby up on your lap and he’ll press down into his feet. He might also add some bounces, so prepare yourself!

Up in arms

Your baby is beginning to discover his arms and hands and use them to reach for and bat at objects. Put a rattle in his hand and he’ll grasp it, shake it, and maybe try to put it in his mouth. Right now this grab-and-grasp action is partly intentional, partly reflexive. But the grasping reflex is beginning to fade and your baby will increasingly begin to reach for things with intent.

Senses Development

Sight

Thanks to improved visual tracking abilities, your four-month-old can now follow brightly colored objects on the move. And that ability to focus both far and near continues to improve.

Hearing

This month you may notice that your baby getting quiet and turning to look at you when you’re speaking. Listening is a critical way that your baby explores his environment. Shake a rattle or clap your hands, and your baby might move his eyes toward the sound to determine where it’s coming from.

Touch

From now through the sixth month, your baby will want to touch, feel, and, most of all, mouth everything she encounters. That’s because your baby is curious about everything, but doesn’t have the dexterity to pick up most things. Make sure you have a wide selection of soft toys appropriate for your baby. And be on the ready if your baby reaches for something that’s not safe. Get the object out of sight and quickly replaced with something your baby can and will slobber on happily.

Mental

Fun fact: Your baby’s brain activity is at one of the highest points of his life right now. He’s all about exploration and curiosity, and using all of his senses to build his understanding of the world.

Social

At this age, your baby clearly recognizes you, which provides a nice boost, right, mama? Your smiley, wiggly, babbling babe loves attention and is happy to accept it from anyone and everyone. Now is an excellent time to introduce a babysitter if you haven’t already. Older siblings are favorites of your baby, and they’re probably big fans of their increasingly interactive baby brother or sister this month. After all, it’s always fun to play with a giggly admirer who isn’t yet capable of messing up their toys!

Language

Your baby’s been listening to you, and is now familiar with your words and sounds. You might begin to hear her trying to imitate you. You’ll probably also hear her laughing, which babies begin doing about a month after their first real smile. Right now she’s chuckling to get attention or in response to being tickled. But soon you’ll start to see there’s a sense of humor developing.

Help Your Four-Month-Old’s Development

There are a few things you can do to help your baby's month-by-month development.

• Encourage your child to move and reach by getting a play gym. Brightly colored dangling toys help babies gain strength in the neck and back as they reach up to grab and play.
• Find ways to bring music into your baby's life. Research suggests that early and regular exposure to music impacts infants positively, both intellectually and socially. A good way to share music with your baby is through a music class. Also, you get the opportunity to meet other moms and widen your social circle.
• Look for toys that your little one can shake and bang, such as a rattle or drum. As interest and motor skills develop, these toys are clear favorites.
• Take your baby out into the world and introduce him to new sights and sounds. Your child will benefit from these interactions, and you can break the repetition of day-to-day life with a young baby.
• Be conscious of your baby's crib mobile. Toys that are meant to be watched and not touched can become trouble as babies' motor skills develop and they become interested in reaching and grabbing. Experts recommend removing mobiles when babies start pushing up on their hands and knees, or at four or five months old.

Milestones this Month

Here’s what you can expect your baby to be doing in her fourth month.

• Baby can hold her head up herself when positioned upright.
• Baby's interaction with her world continues, and is beginning to reach for objects in front of her.
• Baby responds to your voice and begins to look in your direction when you call him by name.
• Baby starts to recognize and respond to people familiar to him.

Feeding at Four Months

The exclusively liquid diet continues on this month. Your baby’s bigger stomach means she can eat more at one time, so you should be able to feed less frequently.  Expect your breastfed baby to nurse four to six times a day. Formula-fed babies need five to seven ounces of formula four to six times a day. 

Your baby might demand more frequent feedings again mid-month when she experiences a small growth spurt. And it’s around this time that babies can become easily distracted during feeding time. If this happens, try moving to a quieter spot to help your baby stay focused on the chore at hand: eating!

Sleeping at Four Months

Your baby is still logging 14-16 hours of sleep a day. Thankfully, there’s a good chance she’s showing more predictable patterns, especially when it comes to nighttime snoozing. While she might wake up once (or twice), your baby is capable of sleeping six to eight hours straight at night. If that’s not your experience, check out these sleep tips. At this age, it’s ok to start taking steps – routines, self-soothing, etc. – to help your baby fall asleep on her own.

Common Concerns at Four Months

Growth Charts

A common cause of parental worry at any age is whether their child's height and weight is within an appropriate range. It is important to remember that the growth chart you review with your doctor simply compares your infant with others of the same age and gender. For instance, if your four month old daughter is in the 45th percentile for height, then 45% of girls her age are shorter than her, and 55% are taller.

They are used as a general guide for your pediatrician and are often nothing to worry about. However, you know your baby best, so don't be afraid to talk to your doctor about any concerns you may have.

New Parent Help: "My baby is still so young. Should I play with him?” 

Absolutely! Your little one requires stimulation to help her develop. A lot is going on right now developmentally, and play helps your child mature both physically and mentally. By interacting with your baby and encouraging her to explore her world she'll learn about shapes, colors, and textures. Your baby at 4 months old relies on you to create a safe environment for her to explore. In addition to helping your child develop control of movements and balance, playing with your infant allows you to bond with her. Don't be afraid to be creative, and, most importantly, have fun!

What's Next? Click here to learn about month by month baby development - 5 months old.