As the temperatures drop (they soon will!), any good parent will have plenty of coats and other winter accessories to keep their children warm. Its what we do as parents. Something some parents don't realize is while they need bundled up outside the car, inside the car seat they need to ditch that winter coat! The reason coats aren't safe in the car seat is because, though you may tighten the straps so it passes the "pinch" test with the coat on, the thickness of the coat will compress in a car crash, leaving slack in the harness that wasn't there before.
In the picture above you can see the difference in thickness between the coat normally, and those inches of slack that can happen from the compression, even if it is a little bit, it is just enough to cause the child to be possibly thrown from their car seat, and potentially the vehicle as well.
Another thing to keep in mind is that some products meant to keep baby warm in the car also aren't safe. Snow suits, swaddles, bundleme's and similar. Any fluff can compress and be a dangerous.
Bright side is, it is not needed! Once the car does warm up, your child will probably get too hot (and cranky!) from having their coat on. Think about it, ten minutes into your drive, you take your coat off because you get too hot, your child will get warm too. And they aren't able to take their coat off if it is under the harness.
So what is a parent to do? They need warmth outside the car, but no coats, snowsuits or other thick layers inside the car.
Luckily today, there are many great options! 1) There is the option to warm up the car ahead of time, then wrap a blanket around baby to go to the car. 2) Babywearing! I am a huge fan of babywearing! With my child, I just put him in the baby wrap or carrier, and wrap my husband’s big coat around us both! We stayed warm outside the car, and didn't have a coat to be unsafe in the car. (Some colder climates may not be as efficient) 3) Blankets. Keep some stored in your car to put over the child and harness. If they get too warm, they can always take it off themselves. 4) You can also put their coat on backwards OVER the harness. They will be warm and safe, and can take it off as well if they get too warm! 5) There are great and SAFE products out there now for this reason: - There is the Car Seat Poncho that they can wear inside and outside the car. - "Shower cap" style covers, such as the Cozy Cover, that go over the top of the seat but don't interfere with the harness or go behind the child. (this should still be removed once the child is in the car to reduce the risk of covering baby’s face, or keeping baby too warm) -There is also the Noggle (which is really great for winter and summer) that is an extended for your vents so that heat and a/c can better reach children in the backseat.
The Car Seat Lady has a great post about alternatives to big coats in the car. http://thecarseatlady.com/warmandsafe/
If you have a thin coat that you think may be thin enough that it won’t be a problem, test it before you ever put the car into drive. Simply buckle them in with it on, tighten it properly and WITHOUT loosening the straps, unbuckle the child and take the coat off. Then rebuckle and do the pinch test again to see if there is any slack now that the coat is off. If there is, then it is not a safe option. If there is no slack, then it is a safe coat to wear. Some fleece coats work well for the car seat.
I hope this article has been helpful and able to give you some good insight and advice when it comes to winter coats in car seats, as well as some safe alternatives. For more information or if you would like to schedule a car seat check to ensure your child is safe, you can find a certified Child Passenger Safety Technician in your area at cert.safekids.org.