Winter coat in the car seat? How to keep your baby warm and safe

When the cold sets in, it feels like the obvious thing to do: zip up the coat, into the car and into the car seat. But a thick winter coat and a car seat don't mix. The American Academy of Pediatrics puts it simply: bulky clothing, including winter coats and snowsuits, should not be worn under the harness.

In this article we explain why, how to check in ten seconds whether the harness is snug enough, and how to keep your baby warm in the car without compromising on safety.

Why a coat is a problem in the car seat

A puffy coat is full of air. When you buckle the harness over it, it may feel snug, but in a crash that padding compresses instantly and leaves a gap between the straps and your child's body. With a loose harness, your child can move further than they should and could even slip out of the straps.

That's why tightening the harness with the coat on isn't enough: you're tightening it around the coat, not around your child.

The pinch test: check the harness in ten seconds

1. Sit your child in the car seat and buckle the harness as usual.
2. Tighten the straps until they feel right.
3. Try to pinch the strap vertically at shoulder level.
4. If you can grab a fold of webbing between your fingers, it's too loose: keep tightening until you can't pinch any slack.

Do it every time, coat or no coat. And if you want to check whether a piece of clothing is too thick: buckle your child in wearing it and tighten the harness; then, without touching the straps, take it off and buckle up again. If you can now pinch the strap, that item shouldn't go under the harness.

How to keep your baby warm in the car without a coat

1. Thin layers underneath

Start with close-fitting clothes: a long-sleeved bodysuit, tights or leggings, then trousers and a top or jumper. If it's very cold, add a thin fleece. As a rule of thumb, babies need one more layer than an adult.

2. Warm layers go over the harness

Once the harness is buckled and snug, the warmth goes on top: a blanket over the straps, the coat put on backwards with arms through the sleeves, or a car seat poncho. It keeps your baby just as warm without interfering with the harness. Make sure it's easy to remove once the car warms up, so your baby doesn't overheat.

3. Hat, mittens and socks

They don't affect the harness and they keep your baby really warm. Bring a spare pair of mittens: wet mittens make little hands colder.

4. Don't let the car seat get icy

If your car seat is the carry type (group 0 or infant carrier), keep it indoors when you're not using it: your baby will lose less heat when you put them in.

What about car seat footmuffs?

The golden rule is the same: nothing thick between the harness and your child's body, and always do the pinch test. Whatever actually keeps your baby warm has to sit over the straps.

That's exactly how we designed the fleece footmuff for group 0 car seats and infant carriers that we make at Jyoko. The base goes into the car seat, with very thin padding, and the harness straps come through its openings, so the harness buckles directly over your baby's clothes. The teddy fleece cover, the part that keeps your baby warm, zips closed over the harness, like a blanket that won't slip off. And once the car has warmed up, you can open the cover in seconds. You'll find every model in our winter footmuffs for car seats category.

If you'd rather use a blanket, our baby blankets collection includes the fleece blanket and swaddle wraps, which go over the harness once it's buckled.

Whatever accessory you choose, check your car seat manual too: some manufacturers specify which accessories can be used with their seats.

Common winter mistakes

• Buckling up with the coat on "just for a short trip". Accidents happen close to home too.
• Loosening the harness because your child is "wrapped up warmer". It should always be just as snug.
• Keeping your child bundled up and covered for the whole journey with the heating on: they can overheat. Uncover them once the car is warm.
• Covering their face with the blanket. Always keep the face clear.

In short

In the car, the coat goes over the harness, never under it. Thin layers underneath, a snug harness checked with the pinch test, and the warm stuff (a blanket, a backwards coat or a footmuff cover) over the straps. To learn more about car seat safety, see our 5-minute car seat checklist and our guide to rear-facing car seats.

Source: American Academy of Pediatrics, HealthyChildren.org, "Winter Car Seat Safety Tips".