Your 4-Month-Old Baby’s Development

Major milestones and everyday tips for your baby at 4 months old

Do you feel like your 4-month-old is a whole new baby at times? You’re not imagining things! The 4-month mark is a big milestone in your little one’s life, thanks to some major brain and physical development milestones. Most babies by this age will have doubled their birth weights (or more) and will be sleeping more solid and longer stretches at night. You may have a more predictable schedule for naps, bedtime, and feedings, so life might feel a little more settled. But fair warning, this month can often include the dreaded 4-month sleep regression. Don’t worry—we’re here to help. Find out what to expect from your 4-month-old.

4-month-old baby milestones and development
Illustration by Joshua Seong, Verywell

Your Growing Baby

By 4 months old, most babies have a hit a pretty significant physical milestone by doubling their birth weight. On average, your little one will weigh at least 13 pounds or more by 4 months old, although every baby is different. If your baby was born prematurely, for instance, they may need a little more time to double their birth weight.

Developmental Milestones

Your baby will become much more active and alert and learn to interact with the world around them. Here are some of the major developmental milestones you can expect at this age. 

Body

  • Rolls over from front to back
  • Sits with support
  • Bears weight when standing on a hard surface
  • Holds a rattle or other baby toys
  • Holds up head and chest
  • Pushes up to elbows when laying on stomach
  • Reaches for objects with one hand
  • Coordinates seeing and movement—spotting something they want, then reaching for it
  • Follows objects moving from side to side with eyes
  • Brings hands to mouth

Brain

  • Learns cause and effect
  • Understands object permanence
  • Improves clarity of eyesight and enjoys looking at more patterns, shapes, and colors
  • Smiles spontaneously, most often at people
  • Enjoys playing and may react with negative emotion, such as crying, if playing stops
  • Mimics facial expressions, such as smiling or frowning
  • Babbles and may try to mimic language, like cooing
  • Recognizes people from a distance
  • Cries in different ways (to communicate hunger, boredom, frustration, sleepiness, etc.)

When to Be Concerned

Although every baby will develop differently, if your little one is displaying any of the following signs or symptoms, be sure to talk to your doctor about them at your baby’s 4-month well-child check-up:

  • Crossed eyes
  • Has gained less than 50 percent of their birth weight
  • Is unable to hold their head up
  • Is not able to sit up at all with support
  • Does not seem to respond to or is uninterested in your face
  • Soft spot that appears to be bulging
  • Doesn’t watch items or people as they move
  • Isn’t smiling

A Day in the Life

This age is a fun time in baby development because it’s the beginning of when your child's personality will start to shine. Your little one is able to express when they are upset, bored, tired, or just cranky—and because they now understand cause and effect, will learn that expressing those new emotions gets a response out of you! Get ready for lots of fun baby tricks as your little one learns to experiment with the world around them.

With the learning of object permanence, your baby now realizes things that are out of sight (like you, a blanket, or a stuffed animal) haven’t really disappeared.

As you might imagine, your baby may need more entertainment and stimulation this month, so try experimenting with these new activities for your daytime routine and playtime:

  • Playmates with hanging toys or mobiles to reach for
  • Bouncy seats with hanging toys they can interact with
  • Going for walks in a stroller or carrier that faces out so your baby can see
  • Playing “peek-a-boo” or “hiding” an object under a blanket to see if they try to uncover it
  • Introducing new toys, such as rattles or other items your baby can hold easily and “play” with
  • Reading together—your baby might seem young, but colorful board books will have a lot of stimulation for your little one to look at
  • Letting them explore on their tummy—put your baby down on the floor or play mat and a few toys in front of them to challenge them to reach for their toys

As you're hanging out, you can encourage your infant’s development by using a baby seat, holding them on your lap, or using a breastfeeding pillow propped behind your baby as they learn to sit. Of course, never leave your baby unsupervised near a pillow, especially as they develop those muscles needed to hold themselves up, because there will be a bit of toppling over that happens in the beginning!

Baby Care Basics

Here are some infant care basics to keep in mind at 4 months old:

  • Burping your baby: They might not need to burp with every single feeding at this age. As your baby is able to sit up more and hold their head up better, they may be able to tolerate feedings without burpings now. Every baby is different though, so if your little one seems uncomfortable or gassy, continue burping after feedings.
  • Preventing bug bites: Most insect repellents are safe to use on your baby once they are 2 months old, but you should always exercise caution and do your best to protect your baby naturally.
  • Practicing sun safety: Babies under 6 months old cannot use sunscreen, so if you will be enjoying outdoor fun in the sun, you should keep your little one in the shade and use protective clothing, such as sun hats.
  • Not giving honey: Babies cannot have honey until they are over 1 year old.
  • Bathing: Just like the past few months, you should aim to bathe your baby every two to three days. Your little one’s skin is still sensitive and too many baths may dry out their skin.

Feeding & Nutrition

Your baby will be eating around 6-7 ounces every four to five hours if they are formula-fed and nursing around six to eight times per 24 hours if they are exclusively breastfed. As your baby starts sleeping longer stretches of time at night and taking more regular naps, expect a drastic change in how frequently they will want to nurse. However, your infant may still have periods when they will want to nurse more often, such as during a growth spurt or when they are sick.

At 4 months old, you may be wondering if you can start introducing solid food to your baby. In the past, doctors commonly advised parents to introduce rice cereal to their babies around 4 months old. Today, however, experts know that there is not one “right” age to start your baby on solids. Many pediatricians advise baby-led feeding, which encourages parents to follow their own baby’s cues to know when the best time is to introduce solids. Some babies may be ready to try solid foods earlier (around 4 months) and some babies may not be ready until closer to 8 months. Every baby is different and it's important to avoid introducing solids too early.

How can you know if your baby is getting ready to try solids? The American Academy of Pediatrics (AAP) recommends looking for the following signs:

  • Your baby is able to hold his or her head up: One of the first signs you should look for is the ability to sit on their own in a high chair, feeding chair, or infant seat with adequate head control.
  • Your baby opens their mouth when food is nearby: Is your infant acting like a baby bird and opening their mouth when food comes their way? Reaching for your spoon as you eat ice cream in front of them? Mimicking you eating at the table while they watch you intently? It might be time for food!
  • Your baby moves food from a spoon: If your baby has no interest in food on a spoon that is offered to them, it might be too soon for solids. If your little one takes an active role in moving the food from the spoon into their mouth, however, they might be ready. 
  • Your baby is big enough: If your little one is at least 13 pounds or more, or has doubled their birth weight, chances are they are also ready for solids.

The AAP recommends exclusive breastfeeding for the first six months of life. This means until your baby is 6 or 7 months old, they should only have breastmilk and nothing else (no water, juice, or solid food of any kind).

After 6 months, you can introduce your baby to solid foods, but the AAP still recommends you continue to offer breast milk until your infant is at least 12 months old. The AAP does not have an official recommendation for when to wean your infant, so it is a personal decision that can be made based on what is best for you and your baby. The World Health Organization recommends nursing for 24 months or longer.

How Long Should You Breastfeed Your Child?

Your Baby's First Foods

If you have a baby who is ready for solid food at this age, it's best to introduce them to fresh, pureed fruit or vegetables. There is no need to start your baby on rice cereal or any other type of grain cereal that was traditionally recommended by doctors.

In fact, the AAP explains there is no medical evidence to support feeding your baby a certain type of food first, such as only giving your baby vegetables first. Babies are born with a natural preference for sweet foods, so you won’t make them more likely to turn away vegetables if you give them fruit first. As you introduce solids into your baby’s diet, keep in mind the following tips:

  • Make your own fresh baby food for the highest level of nutrition.
  • Introduce one food at a time so you can watch your baby in the event they have a reaction to the food.
  • You might need to offer a new food to your baby several times before they accept it.
  • There is no evidence that introducing common allergens, like foods that contain peanuts or allergies, causes allergies to your baby. In fact, studies suggest the opposite might be true and that children who are exposed early may have less chance of developing an allergy.

Sleep

At 4 months old, you might encounter a frustrating experience with your infant, thanks to a sleep regression. Sleep regressions happen during different stages of infancy, with the first one occurring around 4 months. Your baby may have settled into a predictable pattern of sleep by now and suddenly show signs such as:

  • Waking up more frequently at night
  • Refusing sleep or naps
  • Increased irritability

Often, sleep regressions are the result of a “growth spurt” in your baby’s brain and body and are fully temporary, so to deal with a sleep regression, continue to be consistent with your baby’s routine and sleep patterns. Although it may be difficult to stick to your infant’s routine during a sleep regression, it is best to continue laying them down at their normal sleep and nap times and any sleep routines you have established, like a bedtime bath or story.

Some helpful sleep habits to keep in mind at this age include:

  • Lay your baby down awake: As your little one learns more about cause-and-effect this month, they may soon realize that by crying, their parents will come pick them up. You might have to experiment more this month by teaching your infant to self-soothe or fall asleep on their own.
  • Allow pacifier use for naps and bedtime: The AAP still recommends pacifier use with naps and bedtime because pacifier use is associated with a reduced risk of SIDS.
  • Keep on napping: Typical nap schedules at this age include two to three naps, in the morning and afternoon, each lasting around 1 hour to 1.5 hours, although that can vary.

One additional development this month that may affect your baby's sleep is their new ability to roll over from front to back. When your baby is capable of rolling, you will want to reconsider using a swaddle, as the blanket may come untucked or unrolled and pose a risk to your little one. A sleep sack may be more appropriate.

Health & Safety

Your baby will have their 4-month-old well-child visit this month. At this appointment, they will receive all of the same vaccines they received at the 2-month well visit, including the pneumococcal, DTaP, Hib, and polio vaccines as injections and the rotavirus vaccine via the mouth.

The 4-month-old well child visit will also include:

  • Complete physical exam, with special attention to your baby's hips to check for developmental hip dysplasia
  • Examination of your infant's growth and development
  • Review of feeding and sleep schedules
  • Measurement of height, weight, and head circumference
  • Counseling for injury prevention
  • Any questions or concerns you may have about your baby

The next well-child check-up with your pediatrician will be when your baby is 6 months old.

Common health concerns at this age might include colds, stomach bugs that might cause vomiting, or thrush. Here are some tips to keep in mind for caring for your little one through these conditions:

  • Colds: Many babies can have runny noses with green or yellow discharge, but not have an actual sinus infection. Green-colored discharge might just indicate the body is doing its normal function of clearing the sinus and nasal passages. However, if your baby’s cold lasts longer than 10-14 days or has severe symptoms accompanying it, such as a high fever, you should take them to the doctor.
  • Vomiting: If your infant is exclusively breastfed, the best thing you can do for them through a stomach bug that causes vomiting is to continue to try to breastfeed. Breast milk is more easily digestible by babies than electrolyte replacement drinks such as Pedialyte, so breast milk is preferred in any illness with an infant. If your infant vomits after nursing, try shortening the nursing session to five or 10 minutes and waiting a few hours to see if the baby can keep the feeding down. If your baby is not able to nurse or vomits everything up after 24 hours, you should seek medical attention. For formula-fed babies, you can offer 0.5-1 ounce of oral rehydration solution in a bottle or syringe, such as Pedialyte, every 15 minutes for two or three hours. If vomiting occurs, wait 30 minutes and try again. If your baby is able to keep the solution down, you can resume normal formula feeding.
  • Fever: Anytime your infant has a fever over 101 degrees Fahrenheit after 4 months, you should call the doctor, or seek medical attention if vomiting or diarrhea is so severe that your infant shows signs of dehydration, such as no tears when crying, no wet diapers for four to six hours, or is lethargic.
  • Thrush: If your baby has white patches on the inside of her mouth or her tongue, or develops a diaper rash that appears symmetrical on both sides and will not go away with diaper rash cream treatment, it might be thrush. Your doctor can evaluate your baby for thrush and may provide an oral medicine for the mouth or an anti-fungal cream for diaper area infections.

Must Knows

The 4-month mark is an exciting time for you and your baby. The busyness of the newborn stage is being replaced with new milestones for your baby in sleep, growth, feeding, and activity. Try to enjoy this fun month and keep some helpful tips in mind:

  • You are the parent your baby needs: Whether you are a working mom, a stay-at-home parent, or somewhere in between (like work from home jobs!), you should know you are exactly the type of parent your baby needs. At this age, your baby needs routine and reassurance they are loved and cared for and will continue to grow and thrive.
  • Keep a close eye on developmental concerns: This is often the age they can become apparent. If you are dealing with a difficult diagnosis or news about your baby's physical or cognitive development, search for an in-person or online support group of parents who have gone through the same thing you have. Lean into other parents who can help, offer advice, and give you the support you need
  • Congratulate yourself on your journey: If you're breastfeeding and made it this far, you've reached a huge accomplishment. Getting through the first few months of nursing can be the hardest. And if you have successfully chosen another feeding route for your baby, take time this month to reflect on choosing to do what's best for you and your baby. Fed is best and you should never waste time feeling guilty for caring for your little one.
  • Take photos: As your baby learns to sit up more without support in the next month, consider booking a photo shoot or trying your hand at some at-home photography. Now would be a great time to get some adorable smiling shots of your little one—before they are even more mobile!
Your 5-Month-Old Baby’s Development & Milestones
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