When the days turn cold, most parents instinctively bundle up their little ones before heading out — including when placing them in the car seat. It feels natural and caring to keep your baby warm and protected. But here’s the catch: those cozy padded jackets and snowsuits can actually make the car seat unsafe.
It’s a common mistake that even the most attentive parents make. The good news? It’s easy to fix once you know why it happens — and there are safe, warm alternatives that don’t compromise on comfort or safety.
Why bulky jackets are dangerous in the car seat
Car seats are designed to hold your baby snugly in place. The harness must fit close to your baby’s chest and hips so that, in the event of a collision, there’s no room for movement. But when a baby wears a thick jacket or snowsuit, the padding creates a soft, airy layer between the child and the harness straps.
That layer feels snug when you tighten the straps — but in a crash, the padding instantly compresses under the force of impact. Suddenly, there’s several centimetres of space between your baby and the harness. That looseness can lead to your baby moving too far forward, increasing the risk of injury.
In crash tests, even a small amount of slack in the harness has been shown to make a big difference. It’s one of those hidden risks that aren’t obvious until you see it demonstrated — but once you know, you can’t unsee it.
What to dress your baby in instead
The goal is simple: keep your baby warm without adding bulk under the harness. The best way to do that is by dressing in thin, insulating layers. This allows you to buckle the harness directly against your baby’s body, ensuring a tight and secure fit.
Natural fibres like merino wool are perfect for this. Merino is incredibly warm for its weight, meaning it doesn’t need to be thick to provide insulation. It’s also breathable, moisture-wicking, and temperature-regulating — all essential when moving between cold outdoor air and the warmth of a car interior.
A merino wool overall or jacket keeps your baby cozy while allowing the harness to fit exactly as it should. The thin, flexible fabric sits smoothly under the straps, with no risk of compression.

How to keep your baby warm safely in the car
Here’s how to make sure your baby stays warm and safe, step by step:
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Dress in layers. Start with a merino bodysuit or base layer, then add leggings, a jumper, or a lightweight merino overall.
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Secure the harness. Buckle your baby into the car seat without any bulky outerwear. The straps should fit snugly — you shouldn’t be able to pinch any harness webbing between your fingers.
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Add warmth on top. Once your baby is securely buckled, you can place a blanket, poncho, or car seat cover over the straps for extra warmth. This keeps the heat in without compromising safety.
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Check comfort. Merino wool naturally regulates temperature, so your baby won’t overheat when the car warms up. If you’re wearing a jacket yourself, remember they might not need as many layers as you do!
This simple method keeps your child just as warm — and much safer.
Why merino wool is a car seat hero
Merino wool isn’t just warm; it’s smart. The fine fibres trap heat close to the body while allowing moisture to escape, keeping your baby dry and comfortable. It’s also odour-resistant, soft against delicate skin, and naturally stretchy — ideal for babies who love to move.
Unlike synthetic or padded outerwear, merino doesn’t add unnecessary thickness. That means your baby’s harness can stay correctly tightened, offering full protection without sacrificing comfort.
And of course, merino wool is a sustainable choice. It’s renewable, biodegradable, and long-lasting - perfectly aligned with our philosophy at Dear Gaia to care for both children and the planet.
A quick test to check your car seat safety
If you’re unsure whether your baby’s jacket is too bulky, try this simple test:
- Strap your baby into the car seat wearing the jacket. Tighten the harness until it feels snug.
- Without loosening the straps, unbuckle your baby and remove the jacket.
- Buckle them back in with the same harness setting.
- If there’s now extra space between the harness and your baby’s body, the jacket is too thick for safe travel.
This test often surprises parents - but it’s a great visual reminder of how much bulk even a small puffer coat can add.
Safe, snug, and sustainable
At Dear Gaia, we believe safety and sustainability go hand in hand. You shouldn’t have to choose between keeping your baby warm and keeping them safe. That’s why we love merino wool — it’s gentle, breathable, and naturally protective, making it the perfect companion for every car ride, from quick errands to winter adventures.
So next time you’re getting ready to buckle up, remember: Snug harness, thin layers, and warmth on top — not underneath.Your baby stays safe, cozy, and comfortable - the Dear Gaia way. 🌿