I did know that actually, but the car seat is two and a half years old so our manufacturer’s warranty is long gone. There are very few (if any) baby products that are considered “totally safe” and all parents have to make the call on what they feel works for them and their child.

Personally, I don’t feel this is any less safe than using just a blanket, and much safer than a big puffy coat that doesn’t allow you to tighten the straps appropriately. In February, you’ve got to use something, so to each his own. Because my version of this is only two layers of thin fleece and no filler or padding, the straps still fit snuggly even after I remove the blanket.

(If you’re worried about it the warranty on your car seat, check your car seat manual and find out what your specific manufacturer has to say about it.)

http://thecarseatlady.blogspot.com/2011/01/bundle-me-everyone-uses-it-in-car-seat.html