What this is about
Every few months, a pile of tiny clothes goes into a box and the next size comes out of the drawer. That change is easy to see coming. The others arrive with what your baby learns to do: one week the swaddle has to go, and a few months later the footed sleepsuit slides on the kitchen floor.
Most of what changes in the first year follows what your baby can do, not the date. Only two changes come with the calendar: sunscreen from 6 months, and a blanket in the crib after the first birthday.
What changes at each stage
Babies learn to roll, sit, crawl and walk in much the same order, but months apart. Some babies walk alone at 8 months and others at 18, and both are on time, so a baby can be early for one stage and late for the next.
The first year, stage by stage
From birthLyingSleepsuits day and night, and a swaddle for sleep if it helps.
Can start at 2 monthsRollingThe swaddle ends. A sleep bag with the arms out takes over.
About 4 to 9 monthsSitting upFood and drool arrive. A top, pants and a bib take over by day.
About 5 to 13 monthsCrawling and pulling upPants cover the knees, and the feet come out of the sleepsuit.
About 8 to 18 monthsWalkingFirst shoes, once your baby walks outside.
These two go by age
From 6 monthsSunscreen on the skin that clothes and shade leave bare.
From 12 monthsA light blanket may go in the crib.
The first months: sleepsuits day and night
In the first weeks, most babies live in sleepsuits, day and night. A newborn sleeps most of the day, and one sleepsuit is a top, pants and socks that can't ride up or get kicked off. There is no age for outfits. The overalls from the baby shower can go on whenever you like, and many parents start with outings and keep the sleepsuits for home.
For the first 3 months, a newborn wears one light layer more than you would, because a small body loses heat fast.
Rolling ends the swaddle
Swaddling can feel like the only reason anyone is sleeping in the early weeks, which makes parents nervous to stop. It has to stop at the first try to roll, which can come as early as 2 months, because a swaddled baby who rolls onto the tummy can't push up with the arms. From that night your baby sleeps in a sleep bag with the arms out.
Rolling changes diaper time too. A baby who flips over halfway through a change makes a long row of snaps slow going, so many parents move to sleepsuits with a two-way zip that opens from the foot.
Sitting up and first food: tops, pants and a bib
Sitting up often comes around 6 months, and so do food and teeth. Solid food usually starts at about that age, and most babies start teething then too, with enough drool to soak the front of a bodysuit by lunchtime.
This is when a separate top and pants earn their place. A spill means changing half an outfit, and the clean half stays on. A bib does the rest: a soft drool bib through the day, a bigger one for meals, and none for sleep. By now many babies wear outfits in the day and sleepsuits at night.
6 months changes sun care, not summer clothes
Before 6 months, sun care is shade and clothes: the stroller canopy, a tree, a sun hat with a brim and light long sleeves. A young baby's skin is more likely to get a rash from sunscreen, so shade does the work.
From 6 months, a mineral sunscreen goes on the skin that clothes and shade leave bare: the cheeks, the backs of the hands, bare feet. It is a backup, so the hat and the shade stay.
Crawling: covered knees
Crawling starts anywhere from about 5 to 13 months, and about one baby in 25 never crawls on hands and knees at all, shuffling along on the bottom or the tummy instead. Once your baby is on the move, the knees spend the day on rugs, floorboards and the rough carpet at daycare. On a hot day at home, a romper with bare knees is fine, and dirty knees wash.
Good: Soft pants
Soft pants or leggings cover the knees and stretch as your baby crawls. Stiff jeans can wait, because they fight every bent knee.
Not good: A long dress
A knee lands on the hem and stops your baby short. Dresses are easiest before crawling and again once your baby walks steadily.
Good: A bodysuit underneath
It stays tucked in while your baby crawls or gets lifted, so the back stays covered.
Not good: A T-shirt alone
It rides up as your baby crawls and leaves the back bare.
Pulling up to stand: feet out of the sleepsuit
Pulling up on the sofa comes anywhere from about 5 to 11 months, and from then on the feet matter.
Not good: Smooth feet slide
Footed sleepsuits are wonderful in the bassinet, but their fabric soles slip on floorboards and tiles just as your baby pushes up to stand.
Good: Bare feet grip
Footless sleepsuits and pants leave the toes free to spread and hold the floor.
At night the footed ones can stay until the toes press the end. On a cold floor in the day, socks with grip dots do the job.
Shoes start with outdoor walking
Shoes start when your baby walks outside, on ground that can hurt bare feet. That is often weeks after the first steps, because a new walker still rides in the stroller for most of a trip. Shoes put on sooner don't help a baby walk any earlier, and a stiff sole makes it harder, so the first shoes are light and bend at the toes, with socks underneath.
Walking changes the outdoor clothes too. A padded pram suit (a snowsuit) suits a baby who rides in the stroller. A toddler who walks and sits down in the snow needs a waterproof suit over winter boots, and on wet days, rain boots and rain pants for the puddles.
Warmth follows movement as well. A baby sitting still in the stroller needs a little more than the parent pushing it. A toddler who runs around the playground warms up the way you do, and often needs no extra layer until the ride home.
Signs your baby needs the next size
Sizes do follow a calendar of sorts: a new one every few months, and what to buy in each size, and when, depends on the month your baby is born. The label tells you roughly when an average baby outgrows a size. Your baby's clothes tell you when yours has. One brand's 6 months can fit like another brand's 3 months.
Does it still fit?
Good: It fits
Check with your baby lying flat and the legs straight. The toes hide inside the feet, so feel for them through the fabric.
- Cuffs at the wrists
- Snaps close flat
- A little room past the toes
Not good: Too small: time for the next size
A one-piece suit often gets too short in the body before the sleeves do, so watch the snaps and the shoulders when your baby sits.
- Cuffs up the forearm
- Snaps pull apart
- Toes press the ends
Not good: Too big for now
If the next size drowns your baby's hands, it is still too big. A sleepsuit or bodysuit this loose bunches at the neck and twists at the feet, so it waits in the drawer until it fits.
- Sleeves cover the hands
- Loose at the neck
- Empty, floppy feet
The first birthday changes the crib, not the daytime outfit
Turning one is a big day, but the clothes that morning are the same as the day before. The change happens in the crib. Before 12 months, nothing loose goes in the crib with your baby. After the first birthday, a small, light blanket poses little risk for a healthy toddler.
Most parents soon find out that a one-year-old rolls and tosses across the crib all night, and the blanket ends up in a corner within minutes. So the sleep bag usually stays.
Questions parents ask
When do babies stop wearing onesies?
Most toddlers move from bodysuits to T-shirts between 12 and 24 months, once walking keeps a T-shirt in place. Many keep a bodysuit under the clothes until potty training, for a warm back on cold days and a diaper that stays put.
When should a baby stop using a sleep sack?
There is no age. An arms-free sleep bag can be used for as long as it fits, and most families stop when the child moves to a bed with a blanket, often at 2 or 3. For a toddler who walks, a sleep bag with legs is easier until then.
When can my baby wear pants?
From the first day, if you like. Footed pants keep a newborn's feet warm with no socks to kick off. Choose soft ones with a wide waistband, cut loose enough for a full diaper.
When do babies grow out of newborn clothes?
For an average baby, within a few weeks: newborn size fits up to about 4 kg (8 to 9 lb). A big baby may skip it, and many babies wear 0–3 months from the first day with the cuffs rolled up.
