Sleeping bags that go in the car seat, even if they have holes cut out for the straps, are not safe as they can interfere with the placement of the straps on the child’s body and the snugness of the straps (by adding extra bulk). The The Bundle Me – everyone uses it in the car seat – but did you know it’s NOT SAFE for car seats (and using it VIOLATES the car seat’s instructions)!” use of these products violates the manufacturer’s instructions to almost every car seat on the market. You can very simply modify these products to make them safe – by cutting out the fabric that goes behind the child’s body and under the straps.
Note: many of these products have filler, so you will need to sew the new edges after cutting otherwise the baby could choke if they tried to eat the filler.
[youtube http://www.youtube.com/watch?v=-MrwoFJc1qs?rel=0&hd=1]