At four weeks old, your baby is just starting to emerge from the sleepy newborn phase. You’ll notice longer stretches of alertness, more eye contact, and the very beginnings of social interaction. This is also a period of rapid physical growth, with most babies gaining about 1.5 to 2 pounds per month. Here’s what’s happening week by week and what to look for.
How Much Your Baby Is Growing
Four-week-old babies are in one of the fastest growth phases of their lives, putting on roughly 1.5 to 2 pounds each month. By now, most babies have regained any weight lost after birth and are starting to fill out. You may notice their face getting rounder, their thighs getting chubbier, and their newborn clothes fitting more snugly.
A growth spurt is common right around this time. The typical infant growth spurts happen at 2 to 3 weeks and again at 6 weeks, so your baby may be finishing one or gearing up for the next. During a spurt, expect your baby to seem hungrier than usual, want to feed constantly (called cluster feeding), and act fussier. These spurts usually last up to three days and then settle down on their own.
Feeding at Four Weeks
Breastfed babies at this age typically nurse 8 to 12 times in 24 hours, roughly every 2 to 4 hours. Some babies cluster feed, nursing as often as every hour for a stretch, then sleeping for a longer 4- to 5-hour window. This is normal and doesn’t mean your milk supply is low. Formula-fed babies generally eat slightly less often because formula takes longer to digest, but the overall pattern of frequent, small meals is the same.
A reliable way to tell if your baby is getting enough is diaper output. After the first week of life, a well-fed baby produces at least 6 wet diapers per day. Stool frequency varies more, especially among breastfed babies, but consistent wet diapers are the simplest sign that hydration and intake are on track.
What Your Baby Can See and Hear
Your baby’s vision is still limited. Newborns see most clearly at a distance of about 8 to 12 inches, which happens to be the distance between your face and theirs during feeding. High-contrast patterns (black and white stripes, bold shapes) are easier for them to focus on than soft pastels. You can test your baby’s developing tracking ability by holding a bright toy about a foot from their face and moving it slowly side to side. At four weeks, they may follow it briefly before losing interest.
Hearing is more developed than vision at this stage. Your baby will turn their head toward the sound of your voice, and they already prefer familiar voices over unfamiliar ones. Loud, sudden noises will startle them, which is a healthy reflex.
Early Social and Physical Skills
Four weeks is right on the edge of some exciting milestones. True social smiling, where your baby smiles in response to your face or voice rather than reflexively, typically starts between 4 and 8 weeks. You might catch a fleeting grin now, though it can be hard to tell if it’s intentional or just a reflex. Over the next few weeks, those smiles will become unmistakable.
Physically, your baby is building neck strength. They can’t hold their head steady yet, so you still need to support it whenever you pick them up. But during tummy time, you may see them briefly lift their head or turn it from side to side. By two to three months, most babies can hold their head steady without support while being held upright, push up onto their forearms during tummy time, and bring their hands to their mouth. These skills are being built right now, even if they’re not fully visible yet.
Early cooing sounds (“oooo,” “aahh”) typically appear in the coming weeks. For now, your baby communicates mostly through crying, grunting, and body movements. They’re also starting to make sounds back when you talk to them, so keep narrating your day. It matters more than it seems.
Sleep Patterns at One Month
A four-week-old sleeps about 16 hours a day, but those hours are broken into short chunks of 2 to 4 hours, scattered across day and night. About half of your baby’s sleep is active (REM) sleep, which is why you’ll see twitching, eye movement, and irregular breathing that can look alarming but is completely normal.
Your baby’s stomach is still tiny, so they need to wake every few hours to eat. Most babies don’t sleep through the night (a stretch of 6 to 8 hours) until at least 3 months of age, or until they weigh 12 to 13 pounds. If your baby occasionally has one longer stretch of 4 to 5 hours, that’s fine, but don’t expect it to be consistent yet. Day-night confusion is still common at four weeks. Exposing your baby to natural light during the day and keeping nighttime feedings dim and quiet can help their internal clock start to sort itself out.
Why the Crying Is Increasing
If your baby seems to be crying more than they did in the first week or two, you’re not imagining it. Babies enter a phase sometimes called the Period of PURPLE Crying, which begins around 2 weeks of age and peaks during the second month of life. During this phase, crying can last several hours a day (five hours or more for some babies), often clusters in the late afternoon and evening, and may resist every soothing technique you try. Your baby may look like they’re in pain even when nothing is wrong, and the episodes can seem to start and stop without any clear trigger.
This phase is a normal part of nervous system development, not a sign that something is wrong with your baby or your parenting. It typically tapers off by 3 to 5 months. In the meantime, cycling through soothing strategies (swaddling, white noise, gentle rocking, a pacifier) helps some babies. When nothing works, it’s okay to set your baby down in a safe place like their crib and take a few minutes to collect yourself.
Safe Sleep Basics
The American Academy of Pediatrics recommends placing your baby on their back for every sleep, including naps. Use a firm, flat mattress in a safety-approved crib or bassinet, covered only by a fitted sheet. Keep the sleep area in your room, ideally for at least the first six months.
Nothing else belongs in the crib: no blankets, pillows, bumper pads, or stuffed animals. If you’re worried about your baby being cold, use a sleep sack or wearable blanket instead of loose bedding. Signs your baby is too warm include sweating or a chest that feels hot to the touch. Offering a pacifier at sleep time is also associated with reduced risk, and if you’re breastfeeding, you can introduce one once breastfeeding is well established, which for many families happens right around this four-week mark.
The One-Month Checkup
Most pediatricians schedule a well-child visit at one month. Your baby’s doctor will measure weight, length, and head circumference and plot them on a growth chart. This visit is less about hitting specific milestones and more about confirming a healthy growth trajectory. Your baby may receive the second dose of the Hepatitis B vaccine if the first was given at birth.
This appointment is a good time to bring up anything that’s been on your mind: feeding concerns, sleep questions, unusual rashes, or how you’re coping emotionally. Pediatricians expect these questions at the one-month visit, so don’t hold back.
What the Day-to-Day Actually Looks Like
At four weeks, there’s no real “schedule” yet. Your days revolve around feeding, changing, soothing, and brief windows of alertness where your baby stares at your face, looks around the room, or quietly takes in their surroundings. Those alert windows may only last 30 to 60 minutes before your baby is ready to sleep again.
Tummy time can start now if it hasn’t already, even just a few minutes at a time on your chest or on a blanket on the floor. Your baby will probably protest, but short sessions build the neck and shoulder strength they need for every physical milestone ahead. Bath time, a short walk outside, or simply holding your baby skin-to-skin all count as meaningful interaction at this age. You don’t need to “do” much. Being present and responsive is the most important thing happening right now.