A long-sleeve bodysuit is a soft top with sleeves to the wrists that snaps closed under the diaper. Most are cotton. It is the first layer on your baby's skin. Arms, belly and back stay covered, and nothing rides up when you lift your baby.
US shops call it a long-sleeve onesie, UK shops a long-sleeve vest, and much of Europe a body. Apart from the sleeves, it is the same garment as the short-sleeve bodysuit.
- For ages0–24months
- You'll need4–7per size
- Wear it below24°C75°F
When babies wear one
Below 24°C (75°F), it is where almost every outfit starts. Indoors it goes with pants and socks. As it gets colder, a cardigan, fleece or jacket goes on top, one layer at a time.
On cool nights it goes under a sleepsuit, or alone inside a sleep bag. Once the weather turns hot, switch to short sleeves or a romper.
Types of long-sleeve bodysuit
They differ in how they go on.
Envelope neck
The usual kind. It goes on over the head, and the overlapping shoulders let the neck stretch wide. It works from birth.
- Good: Snaps only under the diaper
- Not good: Goes on over the face
Wrap bodysuit
Shops call it a side-snap or kimono bodysuit. It opens like a small jacket: one flap crosses over the other and snaps at the side, then it snaps under the diaper as usual. It helps most in the first weeks.
- Good: No pulling over the head
- Good: Opens flat on the mat
- Not good: More snaps to line up
Diaper shirt
Cut like the wrap bodysuit, but it stops at the hips. US shops sell it as a side-snap or kimono shirt.
- Good: No snaps under the diaper
- Good: Quick for a diaper change
- Not good: Rides up when you lift your baby
Mitten cuffs
Many newborn-size long-sleeve bodysuits have a flap at each wrist that folds over the hand like a mitten. It keeps sharp newborn nails off the face, and unlike separate scratch mittens it cannot fall off in the night.
Folded over
For sleep, or while your baby keeps scratching. Before you fold it, look inside for loose hairs or threads, because a hair can wind around a tiny finger.
Folded back
For awake time, so your baby can touch, grasp and suck on both hands.
How to choose a long-sleeve bodysuit
1. Sleeves that sit close
Every layer you add goes on over this sleeve, so it has to slide into the next one without bunching up at the elbow. A slightly long sleeve can be folded back once.
- Good: Cuff ends at the wrist
- Good: Sleeve follows the arm
- Not good: Wide sleeve, bunched at the elbow
2. Room in the body
Go by your baby's length and weight, because the age on the label is only a rough guide. Size up as soon as the body is tight, even when the sleeves still fit.
- Good: Bottom snaps meet with no stretch
- Good: Length and weight match the label
- Not good: Snaps strain over the diaper
3. Fine wool for cold days
Cotton suits most days. For a cold house or long winter outings, fine merino wool, alone or mixed with silk, is the warmer choice. It costs more. For a toddler playing in the snow, the two-piece version is thermal underwear.
- Good: Merino, or merino and silk
- Good: Warm when a little damp
- Not good: Wool cycle or hand wash only
How to put on a wrap bodysuit
Your baby lies on the changing mat the whole time, and nothing goes over the head.
1. Lay it open
Undo every snap, spread both flaps out to the sides and lay your baby on the back of the bodysuit.
2. Bring each hand through
Bunch the sleeve up in your hand, slip your fingers in at the cuff, find your baby's hand and guide it out. It is easier than pushing the arm in from the shoulder.
3. Bottom flap, then top flap
Snap the flap that goes underneath at its side first. Then cross the top flap over it and snap it down the other side. Finish with the snaps under the diaper.
Questions parents ask
Do newborns wear long sleeves in summer?
On warm days, yes, a thin one. At 24–27°C (75–81°F), a baby under 3 months wears a thin long-sleeve bodysuit and light pants, because a thin sleeve covers young skin without trapping heat. Older babies change to short sleeves. From 28°C (82°F), one short-sleeve bodysuit or a romper is the whole outfit.
Should I buy long-sleeve or short-sleeve bodysuits?
Both, in a mix that follows the season. A baby born in autumn or winter wears long sleeves almost every day. A summer baby wears them on cooler days, and in the first three months on warm days too.
Do you put a onesie under a sleep sack?
Yes, depending on the room temperature. At 18–21°C (64–70°F), a long-sleeve bodysuit goes under the sleep bag, because most sleep bags leave the arms out. At 22–27°C (72–81°F), short sleeves are enough, and from 28°C (82°F) your baby sleeps in a diaper with no bag.
Is a long-sleeve onesie and a swaddle too hot?
Only in a warm room. Under a swaddle, long sleeves suit a room at 20–21°C (68–70°F), short sleeves 22–23°C (72–73°F), and a diaper alone 24–27°C (75–81°F). From 28°C (82°F), leave the swaddle off.
Are side-snap onesies better for newborns?
Easier in the first weeks, but not necessary, even for the cord stump. Fold the diaper down below the stump and avoid tight clothes, so air reaches it. Any bodysuit that sits loosely over the belly does that.
Do babies need mitten cuffs?
Not always. Mittens are rarely needed, because short nails prevent most scratches: trim or file them once a week or more. If scratching goes on, cover the hands only for sleep, which a mitten cuff makes easy.
My baby has eczema. Do mitten cuffs help?
They can. Short nails and anti-scratch mittens help a baby with eczema, because scratching then does less damage to the skin. Cuffs are mostly sold in the first sizes, so an older baby may need separate scratch mittens.
Are merino or wool-silk bodysuits itchy?
Fine merino usually is not. Wool prickles when its fibers are thick and stiff, and merino made for the skin is spun from much finer ones. For skin with eczema, cotton is the usual first choice, but fine merino suits many babies with eczema too. Try one piece first, and go back to cotton if the skin turns red or itchy.
Is a long-sleeve onesie the same as a sleeper?
No. A long-sleeve bodysuit ends at the diaper, like a top, so it goes with pants and socks. A sleeper, called a sleepsuit in the UK, has legs and usually feet as well.
