A blanket is the obvious thing to buy for a baby, and the one thing current guidance asks you to keep out of the sleep space. That contradiction catches a lot of people out, so it's worth setting out plainly.
What the guidance says
A baby sleeps on their back, on a firm flat mattress, in a space with nothing loose in it. No pillows, no soft toys, no bumpers, no blankets draped over them. In the US, crib bumpers have been banned outright since 2022.
The reasoning is straightforward: anything loose can end up over a baby's face, and babies can't reliably move it.
Guidance is updated periodically and differs a little between countries. Read the current advice where you live — this article is a starting point, not the last word.
So what keeps them warm?
A wearable layer. A sleep sack or sleeping bag is worn rather than laid over, so it can't ride up or be kicked off, and it does the job a blanket used to do without anything loose in the bed.
Three shapes, roughly:
Sleeveless sacks — the standard. Arms stay free, which matters for temperature regulation, and there's a zip for changes without a full wake-up.
Swaddle wraps and cocoons — for the newborn stretch, and for contained naps rather than unattended overnight sleep. Read the product's own guidance here; ours say so explicitly where it applies.
Padded vests and winter layers — for cold rooms, and the category where it's easiest to overdo it.
Warmth is a room problem, not a fabric problem
The useful question isn't "is this warm enough" but "what temperature is the room". A bamboo cotton sleeping bag will carry a room from about 10–20°C. Below that you're layering underneath, not buying something thicker.
Dress the baby for the room, check the back of the neck rather than hands or feet, and take a layer off before adding one.
Then what are blankets for?
Everything else, and that's not a consolation prize. A cotton gauze blanket goes on the stroller, over a lap, under a baby on the floor, across a car seat in a cold garage. Knitted cotton blankets and large bamboo swaddles get more use than almost anything else in the house — just not in the sleep space.
Buy them without guilt. Use them awake.
The short version
- Bare sleep space. Back. Firm, flat mattress.
- Warmth goes on the baby, not over them.
- Dress for the room temperature, and check the neck.
- Blankets are for awake time — and there's a lot of awake time.