HALO DOES NOT recommend using a SleepSack Wearable Blanket that does not correspond to your baby’s current size. The purpose of the wearable blanket is to keep your baby from having any excess material that may bunch up around the baby’s nose or mouth. If the baby is wearing a wearable blanket that is too large, there is a potential for the baby's head to slip through the neck hole or for excess material to bunch up around his or her face.