By 4 months, most babies can hold their head steady, coo and make vowel sounds, smile to get your attention, and track objects with their eyes. These milestones represent what 75% or more of babies can do by this age, so think of them as a general guide rather than a rigid checklist. Every baby develops on a slightly different timeline, but knowing what to look for helps you celebrate progress and spot anything worth mentioning to your pediatrician.
Movement and Physical Skills
Head control is the big physical milestone at 4 months. When you hold your baby upright, they should be able to keep their head steady without wobbling or needing support. During tummy time, most babies this age push up onto their elbows and forearms, lifting their chest off the surface. Some are even starting to roll over, though many won’t master this until closer to 5 or 6 months.
Your baby’s arms and legs are moving with more purpose now. Instead of the random jerky movements you saw in the newborn stage, you’ll notice deliberate kicking and reaching. They can swing their arms at toys dangling overhead, hold a rattle or soft toy when you place it in their hand, and bring their hands (and everything else) to their mouth. A few babies at this age will try to bear weight on their legs when you hold them in a standing position, though that’s on the early side.
Sounds and Early Communication
Four-month-olds are finding their voice. You’ll hear cooing, vowel-heavy sounds like “oooo” and “aahh,” and the beginnings of babbling. Your baby is starting to mimic the rhythm and melody of your language, raising and dropping their voice as if asking a question or making a statement. It sounds like gibberish, but if you listen closely, you can hear the patterns of real conversation underneath it.
This is also the age when babies start “talking back.” When you speak to them, they’ll make sounds in response, creating a back-and-forth exchange. They turn their head toward your voice and may begin reacting differently to your tone. A cheerful, playful voice gets a different response than a firm “no.” Some babies at this age are even starting to recognize their own name, though a consistent response to it typically comes a bit later.
Social and Emotional Development
Your baby’s social world is expanding quickly. At 4 months, they smile on their own to get your attention, not just as a reflex or response to your face. They’ll chuckle (not a full belly laugh yet, but close) when you try to be funny. And they actively work to keep your attention, using eye contact, sounds, and movement together to stay engaged with you.
This is one of the most rewarding phases for parents because the interaction finally feels two-directional. Your baby isn’t just receiving your attention; they’re seeking it out and responding to it with clear emotional reactions.
Vision and Cognitive Growth
By 3 to 4 months, your baby’s eyes work together to focus on and track objects smoothly. They can follow a toy moved across their field of vision, and if you roll a ball across the floor, they’ll likely turn to watch it. Color vision is developing too. Babies this age are starting to distinguish between shades of red, blue, and yellow, which is why high-contrast and brightly colored toys grab their attention.
You’ll notice signs of early problem-solving. If your baby is hungry and sees a breast or bottle, they open their mouth in anticipation. That’s not just a reflex; it’s evidence that they’re connecting what they see with what they know. They also spend long stretches studying their own hands, turning them over, watching their fingers move. Mirrors fascinate them, though they don’t yet understand who they’re looking at. Depth perception is still developing and won’t fully come together until around 5 months.
Sleep at 4 Months
The recommended sleep for babies 4 to 12 months old is 12 to 16 hours per day, including naps. But if your baby was sleeping well and suddenly isn’t, you’re likely experiencing the 4-month sleep regression. This isn’t a setback. It’s a sign of neurological development. Your baby’s brain is transitioning from simple newborn sleep patterns to more mature sleep stages with distinct cycles of light and deep sleep. That reorganization creates temporary instability, meaning more frequent waking, shorter naps, and fussiness at bedtime.
The regression typically lasts two to six weeks. It feels endless while you’re in it, but it’s a normal part of brain development, not a sign that anything is wrong.
Feeding and Nutrition
At 4 months, breast milk or formula remains your baby’s only food source. Formula-fed babies typically take about 6 ounces per feeding, with a daily maximum of around 32 ounces. Breastfed babies regulate their own intake, so feeding on demand remains the best approach.
You might be wondering about starting solid foods. The American Academy of Pediatrics recommends introducing solids at about 6 months, and starting before 4 months is not recommended. Some babies show signs of readiness between 4 and 6 months: sitting with support, good head and neck control, opening their mouth when food is offered, swallowing food instead of pushing it out with their tongue, and reaching for objects. But even if your baby shows a few of these signs early, most pediatricians recommend waiting until closer to 6 months unless there’s a specific reason to start sooner.
Vaccines at the 4-Month Visit
The 4-month well-child visit includes the second round of several routine vaccines. Your baby will typically receive doses protecting against diphtheria, tetanus, and whooping cough; bacterial meningitis; polio; pneumococcal disease; and rotavirus. These are all second doses in a series that started at 2 months, building on the immune protection your baby is already developing.
Signs to Watch For
Because milestones describe what 75% or more of babies can do by a given age, missing one skill isn’t necessarily a concern. But if your baby isn’t doing several of the following by the end of month 4, it’s worth bringing up at your next pediatric visit:
- No head control when held upright
- No cooing or vowel sounds
- Doesn’t smile on their own or in response to you
- Doesn’t track objects with their eyes
- Doesn’t respond to your voice by turning toward you or making sounds back
- Doesn’t push up on forearms during tummy time
- Doesn’t bring hands to mouth or show interest in their own hands
Missing milestones can reflect anything from a temporary lag to a developmental concern that benefits from early intervention. The earlier issues are identified, the more effective support tends to be.